The number and arrangement of electrons in an atom's outer energy level (valence shell) determine the atom's
(a) Atomic weight
(b) Atomic number
(c) Molecular weight
(d) Chemical properties

Verified step by step guidance

1. Understand that the valence shell refers to the outermost energy level of an atom where electrons reside.
2. Recall that the atomic weight is related to the total number of protons and neutrons in the nucleus, not the electrons.
3. Recognize that the atomic number is the number of protons in the nucleus, which defines the element but is not directly about electron arrangement.
4. Know that molecular weight refers to the combined mass of atoms in a molecule, which is unrelated to electron arrangement in a single atom.
5. Conclude that the number and arrangement of electrons in the valence shell primarily determine the atom's chemical properties, as these electrons participate in chemical bonding and reactions.

Key Concepts

Valence Electrons

Valence electrons are the electrons located in the outermost energy level of an atom. They play a key role in chemical bonding and reactions because they can be gained, lost, or shared with other atoms. The number and arrangement of these electrons influence how atoms interact with each other.

Atomic Number

The atomic number is the number of protons in an atom's nucleus and defines the element. It determines the identity of the atom but does not directly describe the chemical behavior, which depends more on the valence electrons.

Chemical Properties

Chemical properties describe how an atom behaves during chemical reactions, including its reactivity and bonding tendencies. These properties are primarily determined by the number and arrangement of valence electrons, which influence how atoms combine to form molecules.