Sbírka 83+ Atom Of Nitrogen Diagram

Sbírka 83+ Atom Of Nitrogen Diagram. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. Seven electrons (white) occupy available electron shells (rings). Feb 15, 2021 · nitrogen number of valence electrons.

Tady Molecular Structure Of A Nitrogen Atom Stock Vector Illustration Of Infographic Properties 201188705

Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. Electron dot diagram of a nitrogen atom. 7), the most common isotope of the element nitrogen.

As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons.

Electron dot diagram also called lewis structure which represents the valence electrons of atoms. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. Electron dot diagram also called lewis structure which represents the valence electrons of atoms. 7), the most common isotope of the element nitrogen. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. The nucleus is composed of protons and neutrons.

The nucleus consists of 7 protons (red) and 7 neutrons (blue)... Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation.. The chemical symbol for nitrogen is n.

So, just represent these 5 valence electrons around the nitrogen atom as a dot... Electron dot diagram also called lewis structure which represents the valence electrons of atoms.

Seven electrons (white) occupy available electron shells (rings).. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. The nucleus consists of 7 protons (red) and 7 neutrons (orange). Feb 15, 2021 · nitrogen number of valence electrons. The chemical symbol for nitrogen is n. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. So, just represent these 5 valence electrons around the nitrogen atom as a dot. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. The nucleus consists of 7 protons (red) and 7 neutrons (blue). 7), the most common isotope of the element nitrogen.. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!

The nucleus consists of 7 protons (red) and 7 neutrons (blue).. The chemical symbol for nitrogen is n. 7), the most common isotope of the element nitrogen. The nucleus consists of 7 protons (red) and 7 neutrons (blue). Laboratory chemical safety summary (lcss) datasheet.. The nucleus consists of 7 protons (red) and 7 neutrons (blue).

So, just represent these 5 valence electrons around the nitrogen atom as a dot. 7), the most common isotope of the element nitrogen. Electron dot diagram of a nitrogen atom. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. 7), the most common isotope of the element nitrogen... The electron configuration of nitrogen(n) and the orbital diagram …

Please visit the nitrogen element page for information specific to the chemical element of the periodic table. The electron configuration of nitrogen(n) and the orbital diagram … As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! Electron dot diagram also called lewis structure which represents the valence electrons of atoms. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). So, just represent these 5 valence electrons around the nitrogen atom as a dot. 7), the most common isotope of the element nitrogen. Please visit the nitrogen element page for information specific to the chemical element of the periodic table. New users enjoy 60% off. 7), the most common isotope of the element nitrogen.. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation.

Please visit the nitrogen element page for information specific to the chemical element of the periodic table. 7), the most common isotope of the element nitrogen. New users enjoy 60% off. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings).

Seven electrons (white) occupy available electron shells (rings). Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. Laboratory chemical safety summary (lcss) datasheet. The chemical symbol for nitrogen is n. Feb 15, 2021 · nitrogen number of valence electrons. So, just represent these 5 valence electrons around the nitrogen atom as a dot. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. Electron dot diagram also called lewis structure which represents the valence electrons of atoms. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. Electron dot diagram of a nitrogen atom. Seven electrons (white) occupy available electron shells (rings). The electron configuration of nitrogen(n) and the orbital diagram …

Laboratory chemical safety summary (lcss) datasheet. Feb 15, 2021 · nitrogen number of valence electrons. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. Electron dot diagram of a nitrogen atom... Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!

The nucleus consists of 7 protons (red) and 7 neutrons (blue)... The electron configuration of nitrogen(n) and the orbital diagram … As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. The chemical symbol for nitrogen is n. 7), the most common isotope of the element nitrogen. I show you where nitrogen is on the periodic table and how to determine.. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons.

Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! Feb 15, 2021 · nitrogen number of valence electrons. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! The nucleus consists of 7 protons (red) and 7 neutrons (blue). 7), the most common isotope of the element nitrogen. New users enjoy 60% off. So, just represent these 5 valence electrons around the nitrogen atom as a dot. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). Electron dot diagram of a nitrogen atom... Electron dot diagram also called lewis structure which represents the valence electrons of atoms.

The nucleus is composed of protons and neutrons. The electron configuration of nitrogen(n) and the orbital diagram … Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). Laboratory chemical safety summary (lcss) datasheet. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. The nucleus consists of 7 protons (red) and 7 neutrons (orange)... Feb 15, 2021 · nitrogen number of valence electrons.

Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation.. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. The nucleus is composed of protons and neutrons. Laboratory chemical safety summary (lcss) datasheet.

7), the most common isotope of the element nitrogen.. New users enjoy 60% off.

Feb 15, 2021 · nitrogen number of valence electrons... .. Feb 15, 2021 · nitrogen number of valence electrons.

Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. . Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation.

The nucleus consists of 7 protons (red) and 7 neutrons (blue)... New users enjoy 60% off. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!.. The nucleus consists of 7 protons (red) and 7 neutrons (orange).

Laboratory chemical safety summary (lcss) datasheet. Electron dot diagram of a nitrogen atom. New users enjoy 60% off. Seven electrons (white) occupy available electron shells (rings). The nucleus consists of 7 protons (red) and 7 neutrons (orange). 7), the most common isotope of the element nitrogen. Please visit the nitrogen element page for information specific to the chemical element of the periodic table. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. The nucleus consists of 7 protons (red) and 7 neutrons (blue).. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation.

Seven electrons (white) occupy available electron shells (rings). I show you where nitrogen is on the periodic table and how to determine. New users enjoy 60% off. Electron dot diagram also called lewis structure which represents the valence electrons of atoms. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings)... Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings).

The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. The nucleus consists of 7 protons (red) and 7 neutrons (orange). 7), the most common isotope of the element nitrogen. The electron configuration of nitrogen(n) and the orbital diagram … Laboratory chemical safety summary (lcss) datasheet. 7), the most common isotope of the element nitrogen. Please visit the nitrogen element page for information specific to the chemical element of the periodic table.

The nucleus consists of 7 protons (red) and 7 neutrons (orange). As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. The nucleus consists of 7 protons (red) and 7 neutrons (orange). I show you where nitrogen is on the periodic table and how to determine. Seven electrons (white) occupy available electron shells (rings). Feb 15, 2021 · nitrogen number of valence electrons. Electron dot diagram also called lewis structure which represents the valence electrons of atoms. Electron dot diagram of a nitrogen atom. The nucleus consists of 7 protons (red) and 7 neutrons (blue).. The nucleus is composed of protons and neutrons.

Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! New users enjoy 60% off. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. The nucleus consists of 7 protons (red) and 7 neutrons (blue). Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. 7), the most common isotope of the element nitrogen. The electron configuration of nitrogen(n) and the orbital diagram … Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). Seven electrons (white) occupy available electron shells (rings).. The nucleus is composed of protons and neutrons.

Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. The chemical symbol for nitrogen is n. Electron dot diagram of a nitrogen atom. Feb 15, 2021 · nitrogen number of valence electrons. I show you where nitrogen is on the periodic table and how to determine. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! The nucleus consists of 7 protons (red) and 7 neutrons (orange). The electron configuration of nitrogen(n) and the orbital diagram … The chemical symbol for nitrogen is n.

The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons... Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! The nucleus is composed of protons and neutrons. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. The electron configuration of nitrogen(n) and the orbital diagram … The nucleus consists of 7 protons (red) and 7 neutrons (orange). Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!

The nucleus is composed of protons and neutrons. Feb 15, 2021 · nitrogen number of valence electrons. The electron configuration of nitrogen(n) and the orbital diagram … Electron dot diagram of a nitrogen atom. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. 7), the most common isotope of the element nitrogen.. So, just represent these 5 valence electrons around the nitrogen atom as a dot.

So, just represent these 5 valence electrons around the nitrogen atom as a dot... Seven electrons (white) occupy available electron shells (rings). Feb 15, 2021 · nitrogen number of valence electrons. The nucleus consists of 7 protons (red) and 7 neutrons (blue). Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. The nucleus is composed of protons and neutrons. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. New users enjoy 60% off. 7), the most common isotope of the element nitrogen. Laboratory chemical safety summary (lcss) datasheet. So, just represent these 5 valence electrons around the nitrogen atom as a dot.. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation.

The electron configuration of nitrogen(n) and the orbital diagram ….. The electron configuration of nitrogen(n) and the orbital diagram … The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). The nucleus is composed of protons and neutrons. I show you where nitrogen is on the periodic table and how to determine. Laboratory chemical safety summary (lcss) datasheet. Please visit the nitrogen element page for information specific to the chemical element of the periodic table. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!. So, just represent these 5 valence electrons around the nitrogen atom as a dot.

Please visit the nitrogen element page for information specific to the chemical element of the periodic table.. Please visit the nitrogen element page for information specific to the chemical element of the periodic table. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). Laboratory chemical safety summary (lcss) datasheet. Feb 15, 2021 · nitrogen number of valence electrons. The nucleus consists of 7 protons (red) and 7 neutrons (orange). The nucleus consists of 7 protons (red) and 7 neutrons (blue). The electron configuration of nitrogen(n) and the orbital diagram … As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. Seven electrons (white) occupy available electron shells (rings)... 7), the most common isotope of the element nitrogen.

The chemical symbol for nitrogen is n. New users enjoy 60% off. Laboratory chemical safety summary (lcss) datasheet. 7), the most common isotope of the element nitrogen. Feb 15, 2021 · nitrogen number of valence electrons. The electron configuration of nitrogen(n) and the orbital diagram … 7), the most common isotope of the element nitrogen. Please visit the nitrogen element page for information specific to the chemical element of the periodic table. So, just represent these 5 valence electrons around the nitrogen atom as a dot. The nucleus consists of 7 protons (red) and 7 neutrons (orange)... 7), the most common isotope of the element nitrogen.

Laboratory chemical safety summary (lcss) datasheet. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation... The nucleus is composed of protons and neutrons.

Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. New users enjoy 60% off. Electron dot diagram of a nitrogen atom. So, just represent these 5 valence electrons around the nitrogen atom as a dot. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure.. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons.

The nucleus is composed of protons and neutrons. The nucleus consists of 7 protons (red) and 7 neutrons (blue). The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. New users enjoy 60% off. The chemical symbol for nitrogen is n. The nucleus consists of 7 protons (red) and 7 neutrons (orange). Electron dot diagram also called lewis structure which represents the valence electrons of atoms. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. Feb 15, 2021 · nitrogen number of valence electrons. I show you where nitrogen is on the periodic table and how to determine. Laboratory chemical safety summary (lcss) datasheet.. The electron configuration of nitrogen(n) and the orbital diagram …

As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons.. The chemical symbol for nitrogen is n... The nucleus consists of 7 protons (red) and 7 neutrons (orange).

The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. The chemical symbol for nitrogen is n. So, just represent these 5 valence electrons around the nitrogen atom as a dot. 7), the most common isotope of the element nitrogen. Electron dot diagram of a nitrogen atom. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!

Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. New users enjoy 60% off. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. Seven electrons (white) occupy available electron shells (rings). I show you where nitrogen is on the periodic table and how to determine. Electron dot diagram of a nitrogen atom. Feb 15, 2021 · nitrogen number of valence electrons. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. Seven electrons (green) bind to the nucleus, successively occupying available electron shells (rings). Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!. Seven electrons (white) occupy available electron shells (rings).

The chemical symbol for nitrogen is n.. Electron dot diagram of a nitrogen atom. The chemical symbol for nitrogen is n.. Please visit the nitrogen element page for information specific to the chemical element of the periodic table.

Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure... The nucleus consists of 7 protons (red) and 7 neutrons (blue).

Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates!. I show you where nitrogen is on the periodic table and how to determine. Electron dot diagram of a nitrogen atom. The chemical symbol for nitrogen is n. New users enjoy 60% off. The nucleus is composed of protons and neutrons. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons. 7), the most common isotope of the element nitrogen.. I show you where nitrogen is on the periodic table and how to determine.

Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. Feb 15, 2021 · nitrogen number of valence electrons. Electron dot diagram of a nitrogen atom. 7), the most common isotope of the element nitrogen. The nucleus is composed of protons and neutrons... Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation.

So, just represent these 5 valence electrons around the nitrogen atom as a dot... Please visit the nitrogen element page for information specific to the chemical element of the periodic table. Nitrogen is an element that has 7 electrons and when we talk about the valence electrons then, valence electrons are those electrons that are present in the outer shell and are associated with molecules or an atom and which also has the capacity to participate in the chemical formation. The electron configuration of nitrogen(n) and the orbital diagram … Laboratory chemical safety summary (lcss) datasheet.. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons.

The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons.. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. I show you where nitrogen is on the periodic table and how to determine. The nucleus consists of 7 protons (red) and 7 neutrons (orange). 7), the most common isotope of the element nitrogen. Feb 15, 2021 · nitrogen number of valence electrons. Electron dot diagram also called lewis structure which represents the valence electrons of atoms. The nucleus consists of 7 protons (red) and 7 neutrons (blue). The chemical symbol for nitrogen is n. Electron dot diagram of a nitrogen atom.. As, from the bohr diagram of nitrogen, we got to know, it has 5 valence electrons.

The electron configuration of nitrogen(n) and the orbital diagram … New users enjoy 60% off. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. Please visit the nitrogen element page for information specific to the chemical element of the periodic table. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. Laboratory chemical safety summary (lcss) datasheet. The chemical symbol for nitrogen is n. 7), the most common isotope of the element nitrogen. So, just represent these 5 valence electrons around the nitrogen atom as a dot. Seven electrons (white) occupy available electron shells (rings).. The nucleus is composed of protons and neutrons.

The electron configuration of nitrogen(n) and the orbital diagram …. Seven electrons (white) occupy available electron shells (rings). The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. Laboratory chemical safety summary (lcss) datasheet.. Electron dot diagram also called lewis structure which represents the valence electrons of atoms.

Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! Seven electrons (white) occupy available electron shells (rings). Laboratory chemical safety summary (lcss) datasheet. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons.. 7), the most common isotope of the element nitrogen.

Electron dot diagram of a nitrogen atom... The nucleus consists of 7 protons (red) and 7 neutrons (blue). The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons.

The electron configuration of nitrogen(n) and the orbital diagram … Electron dot diagram of a nitrogen atom. Please visit the nitrogen element page for information specific to the chemical element of the periodic table. Nov 21, 2020 · nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. Download 53 nitrogen atom diagram stock illustrations, vectors & clipart for free or amazingly low rates! The nucleus consists of 7 protons (red) and 7 neutrons (orange).. Feb 15, 2021 · nitrogen number of valence electrons.