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The atomic number is a crucial concept in chemistry, as it uniquely identifies each element on the periodic table. It represents the number of protons found in the nucleus of an atom. For neutral atoms, the atomic number also equals the number of electrons, because positively charged protons balance negatively charged electrons. This essential property determines an element's chemical behavior and its place on the periodic table.
For example, an atomic number of 7 corresponds to nitrogen, which means nitrogen atoms contain 7 protons and, thus, 7 electrons. Understanding the atomic number allows us to predict an element's electron configuration and, consequently, its chemical properties and reactions.

The electron configuration of an atom describes how electrons are distributed in its atomic orbitals. This is important because the arrangement of electrons determines the chemical properties and reactivity of the element.
Nitrogen, with an atomic number of 7, has an electron configuration of \[1s^2 2s^2 2p^3\]. This means that nitrogen's electrons fill the lower energy levels first—the "1s" orbital, followed by "2s," and then the "2p" orbitals.

• "1s" orbital is filled by 2 electrons.
• "2s" orbital is also filled by 2 electrons.
• "2p" orbital contains 3 electrons.

The outermost shell, known as the valence shell, is key in bonding because these are the electrons available for forming chemical bonds. In nitrogen, there are 5 valence electrons (2s and 2p combined), which play a significant role in its bonding behavior.

Chemical bonding involves the interaction of atoms to achieve stable electron configurations. Nitrogen, with its 5 valence electrons in the \[2s^2 2p^3\] configuration, can achieve stability by forming chemical bonds, either by gaining, losing, or sharing electrons.

• Nitrogen often forms covalent bonds by sharing its valence electrons.
• To complete its octet, it can gain 3 additional electrons, often observed when nitrogen forms anions in ionic compounds.
• Alternatively, it can share its 5 valence electrons with other atoms, achieving a maximum valency of 5.

The maximum valency of an element corresponds to the number of valence electrons it can either gain, lose, or share in a chemical reaction. For nitrogen, this is particularly versatile, allowing it to participate in a wide range of chemical compounds and reactions.