Chemistry Review

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

• Element
• Atom
• Molecule
• Compound

In the atom diagram shown, A is pointing to the darker particles, these are known as

• electrons

• protons

• neutrons

• the nucleus

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 back and forth (move between) two atoms.

• a sea of mobile electrons surround the cations and they then become negativly charged

• valence electrons are transferred from one atom to another, forming charged ions that are then pulled together by attraction between opposite charges

• none of the above

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.

Using the information provided, determine how many electrons the a Boron atom contains.

• 2.5

• 5

• 6

• 10.81