STAAR Review - Category: 1 Matter and Energy

Front

What are the properties of elements in Group 18?

Back

They are gaseous at room temperature and chemically stable.

Front

Why is Fluorine considered the most reactive element?

Back

Fluorine is the most reactive because it has 7 electrons in the outer shell.

Front

Which formulas contain equal numbers of nitrogen atoms?

Back

Formulas I, II, and V.

Front

What is the atomic structure of a zinc (Zn) atom?

Back

A zinc (Zn) atom contains 30 protons inside the nucleus and 30 electrons outside the nucleus.

Front

Which substances have the same number of carbon atoms?

Back

Substances 1 and 3.

Front

What is the definition of a valence electron?

Back

Valence electrons are the electrons in the outermost shell of an atom that are involved in chemical bonding.

Front

What is the significance of the atomic number?

Back

The atomic number indicates the number of protons in the nucleus of an atom and determines the element's identity.

Front

What is a chemical formula?

Back

A chemical formula is a way of expressing the composition of a substance using symbols for its constituent elements.

Front

What is the difference between an element and a compound?

Back

An element is a pure substance made of only one type of atom, while a compound is made of two or more different types of atoms chemically bonded together.

Front

What does it mean for an element to be chemically stable?

Back

A chemically stable element has a full outer electron shell, making it less likely to react with other elements.