09 Atomic Structure PRE-Assessment

An atom is the smallest unit of matter that retains the properties of an element.

Protons are positively charged particles found in the nucleus of an atom.

Neutrons are neutral particles found in the nucleus of an atom.

Electrons are negatively charged particles that orbit the nucleus of an atom.

The atomic number is the number of protons in the nucleus of an atom.

The mass number is the total number of protons and neutrons in an atom's nucleus.

Valence electrons are the electrons in the outermost shell of an atom that determine its reactivity.

A reactive atom is one that can easily form bonds with other atoms due to its valence electrons.

Aluminum is least reactive because it has 3 valence electrons.

The atomic number is equal to the number of protons in an atom.