Exploring Atomic Structure

The smallest unit of an element is called a ___.

• atom

• molecule

• ion

• compound

In an atom, protons are found in the ___.

• neutron layer

• electron cloud

• valence shell

• nucleus

The charge of a neutron is ___.

• 0

• +2

• -1

• +1

The atomic number of an element is determined by the number of ___.

• nuclei

• electrons

• protons

• neutrons

Electrons are located in ___ around the nucleus.

• clouds

• shells

• orbitals

• layers

The mass number of an atom is the sum of ___ and ___ in the nucleus.

• electrons and protons

• neutrons and electrons

• quarks and leptons

• protons and neutrons

Isotopes of an element have the same number of ___ but different numbers of ___.

• protons; electrons

• neutrons; electrons

• protons; neutrons

• electrons; protons

Which particle has a positive charge? (a) Electron (b) Proton (c) Neutron

• Proton

• Gamma particle

• Beta particle

• Alpha particle

What is the relative mass of an electron? (a) 1 (b) 0.0005 (c) 1.007

• 0.0005

• 1.5

• 0.1

• 0.002

The nucleus of an atom contains ___ and ___.

• protons and neutrons

• photons and neutrinos

• quarks and leptons

• electrons and positrons