Problem 6 - Chemistry The Molecular Nature of Matter

Question

Using the symbol for nitrogen, \({ }_{7}^{14} \mathrm{~N}_{2}^{0},\) indicate what information is conveyed by the two superscripts, and what information is conveyed by the two subscripts.

Step-by-Step Solution

Answer

The superscripts represent the atomic mass number (14) and the electric charge (0); while the subscripts represent the atomic number (7) and potentially the number of atoms in the molecule (2), though the latter is unconventional in isotope notation.

Step 1: Identify Information Conveyed by the Superscripts

The two superscripts in the symbol \( { }_{7}^{14} \mathrm{~N}_{2}^{0} \) represent the atomic mass number and the charge number, respectively. The atomic mass number (14) is the total number of protons and neutrons in the nucleus of the atom. The charge number (0) indicates that the nitrogen atom is electrically neutral, with no excess charge.

Step 2: Identify Information Conveyed by the Subscripts

The two subscripts in the symbol \( { }_{7}^{14} \mathrm{~N}_{2}^{0} \) indicate the atomic number and the number of atoms in the molecule, respectively. The atomic number (7) specifies the number of protons in the nucleus of the atom and thereby identifies the element as nitrogen since nitrogen has 7 protons. The subscript after the element symbol (2), which is not commonly used in this context, would typically suggest the molecule consists of two nitrogen atoms, referring to the diatomic nature of the nitrogen molecule in its natural form.

Key Concepts

Understanding Atomic Mass Number

Atomic mass number is fundamental to the study of chemistry. It represents the total count of protons and neutrons within an atom's nucleus. Protons and neutrons are nearly equal in mass, and together, they constitute the majority of an atom's mass.

For example, in the nitrogen symbol { }_{7}^{14} N, the superscript '14' is the atomic mass number. Nitrogen atoms have 7 protons (as indicated by its atomic number) and 7 neutrons, giving us a total of 14, which is the atomic mass number. This is pivotal in understanding the isotopic composition of an element since isotopes of an element have the same number of protons but different numbers of neutrons, hence different atomic mass numbers.

The Significance of Atomic Number

The concept of atomic number is a cornerstone in identifying an element. It is denoted by the subscript found to the lower left of an element's symbol and indicates the number of protons in an atom's nucleus. Importantly, the atomic number defines the chemical identity of an element.

In our nitrogen example { }_{7}^{14} N, the subscript '7' tells us that there are 7 protons in the nucleus. The existence of a unique number of protons is what makes each element distinct. Thus, regardless of how many neutrons or electrons an atom may have, if it possesses 7 protons, it will be recognized as nitrogen.

Diatomic Molecules: Nature's Preference for Pairs

Diatomic molecules are those composed of only two atoms, which may be the same (homodiatomic) or different (heterodiatomic). Many nonmetal elements naturally occur as diatomic molecules, including hydrogen (H_2), oxygen (O_2), and nitrogen (N_2).

The subscript '2' in the nitrogen molecule symbol { }_{7}^{14} N_2 indicates that two nitrogen atoms bond together to form a diatomic molecule, which is the most stable form of nitrogen under normal conditions. Understanding this concept is useful for grasping why certain gases are diatomic and for predicting the behavior of elements in chemical reactions.

Electric Charge: The Balance of Power

Electric charge is the property of matter that causes it to experience a force when near other electrically charged matter. It is represented by the superscript placed to the far right of the element's symbol.

In the nitrogen example, the superscript { }^{0} after N indicates a neutral charge, meaning there are equal numbers of protons and electrons. This neutrality is integral to the stability of atoms. When atoms gain or lose electrons, they become ions with a positive or negative charge, affecting their chemical reactivity. By indicating the charge, chemical symbols provide insight into an atom's potential to engage in ionic bonding and participate in electrically-driven chemical processes.