Chemistry Unit review

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

• Element
• Atom
• Molecule
• Compound

Answer explanation

An atom is the smallest basic unit of Matter.

An element is made of only one type of atom.

Atoms are made from electrons, protons and neutrons.

Elements can combine with each other to form molecules

In the atom diagram shown, E is pointing to

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

What charge does an electron have?

• Negative
• Positive
• Neutral
• Contrated

In this chemical equation, the elements in red are the_______.

• Products

• Reactants

• Subscripts

• Coefficients

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.

Which of the following is true about elements?

• All chemicals are elements.
• Elements are pure substances that can't be broken down.
• Elements can be broken down chemically or electrically.
• Elements are made of more than one substance.

What clues tell you that a substance is a compound?

• It is made of one substance.
• It can't be separated.
• It is made of a mixture of elements.
• It has a formula.

Sugar is added to water, and the mixture is stirred. What type of mixture has been created?

• A homogeneous mixture.

• A plain mixture.

• A heterogeneous mixture.

• A complex mixture.

Answer explanation

A homogeneous mixture means a substance which dissolve in water.Sugar dissolved in water.So sugar is a homogeneous mixture.

A chemist is looking for an element that reacts similarly to the element lithium (Li). What would you tell the chemist to look for on the periodic table?

• Look for similarities in the mass. Elements in groups will act the same as other elements in the group.

• Look for any metal.

• Its neighbor to the bottom (sodium) has similar properties to lithium because trends in groups behave very similarly to each other.

• Nothing is similar

Which of the following elements is the most reactive?

• strontium (Sr)

• calcium (Ca)

• beryllium (Be)

• magnesium (Mg)

Answer explanation

Group 17 are the most reactive of all elements