8th Grade Science Review

What is the role of mRNA in protein synthesis?

• it makes the bases that makes up DNA

• it transcribes the code from DNA

• it helps DNA perform replication

• it makes the amino acids used in protein synthesis

The table shows the number of neutrons, protons, and electrons for two atoms. How are the two atoms alike?

• They have the same charge.

• They have the same mass number.

• They have the same atomic number

• They are atoms of the same element.

The diagram shows the arrangement of electrons in a neon atom. How many protons are present in this atom's nucleus?

• 10

• 8

• 2

• There is not enough information to answer this question.

In the diagram, the arrows labeled III point to the atom's ______________.

• Protons

• Neutrons

• Nucleus

• Electrons

Elements with seven valence electrons —

• are highly reactive

• are highly stable

• have a high mass

• have a low mass

The atoms of a certain element each contain 11 protons and 1 valence electron. Which statement correctly identifies this element and describes its chemical reactivity?

• The element is sodium, and it is highly reactive

• The element is fluorine, and it is highly reactive

• The element is sodium, and it is not very reactive

• The element is fluorine, and it is not very reactive

Which of these elements would have properties most similar to arsenic (As)?

Use the periodic table and your notes slides.

• Silicon (Si)

• Selenium (Se)

• Tin (Sn)

• Phosphorus (P)

Sulfur is a nonmetal. Of the following, the physical characteristic that is most

likely to describe a sample of sulfur is —

• a shiny appearance

• brittleness

• malleability

• ductility

How many of each atom are in the compound above?

• 1 magnesium atom, 2 iron atoms, and 4 oxygen atoms

• 3 magnesium atoms, 2 iron atoms, and 4 oxygen atoms

• 6 magnesium atoms, 6 iron atoms, and 12 oxygen atoms

• 3 magnesium atoms, 6 iron atoms, and 12 oxygen atoms

Potassium nitrate is a compound used in some fertilizers. Its chemical formula

is KNO3. How many TOTAL atoms are in each unit of potassium nitrate?

• 2

• 5

• 3

• 9