Chemistry Review

Which of the following is described as the basic unit of matter?

• Element
• Atom
• Molecule
• Compound

In the atom diagram shown, E is pointing to

• An electron
• a proton
• a neutron
• the nucleus

A molecule is________

• two ions held together by opposite charges
• smaller than an atom
• can be physically separated into smaller atoms
• more than one atom bonded together by covalent bonds

What charge does an electron have?

• Negative
• Positive
• Neutral
• Contrated

Which of the following is found in the nucleus of an atom?

• electrons
• neutrons
• The center of an atom, composed of protons and neutrons
• molecules

What is the atomic mass of this atom?

• 1

• 3

• 4

• 7

What is the atomic number of this atom?

• 4
• 5
• 9
• none of the above

What is a valence electron?

• an electron that is found in the outermost orbital of an atom. 
• an electron found in the innermost orbital of an atom.
• an electron found in the middle orbital.

An ionic bond forms when 

• Valence electrons are shared
• a sea of mobile electrons surround the cations
• valence electrons are transferred between atoms
• none of the above

In chemical compounds, covalent bonds form when

• the electronegativity difference between two atoms is very large.
• electrons are completely transferred between two atoms.
• pairs of electrons are shared between two atoms.
• ions are held together by opposite charges.