Test 1 Practice

Which statements describe how the atomic theory has developed over time?

• Atomic theory has changed as new discoveries were made.

• Contributions from different scientists have improved atomic models.

• The atomic model has always remained the same.

According to the modern atomic model, electrons –

• occupy regions of space called electron clouds

• orbit the nucleus in fixed circular paths

• can be seen using high-powered microscopes

• stay motionless around the nucleus

Why do scientists use diagrams or models to describe atoms?

• Atoms are too small to be directly observed with the human eye.

• Models give a perfect picture of an atom’s shape.

• Scientists prefer models over real evidence.

Which element is most likely to react in a similar way to magnesium?

• Calcium

• Sodium

• Neon

• Iron

Our current understanding of atomic structure is considered a scientific theory because –

• it is supported by repeated evidence and observation.

• it is a single scientist’s opinion about atoms.

• it cannot be tested or changed over time.

Carbon-12, Carbon-13, and Carbon-14 are examples of isotopes because they –

• have the same number of protons but different numbers of neutrons.

• have the same number of neutrons but different protons.

• contain a different number of electrons.

Four atoms are shown below: Atom A: 7 protons, 7 neutrons, 7 electrons Atom B: 7 protons, 8 neutrons, 7 electrons Atom C: 8 protons, 8 neutrons, 8 electrons Atom D: 6 protons, 7 neutrons, 6 electrons Which two atoms represent the same element?

• A and B

• A and C

• B and D

• C and D

Calcium has an atomic number of 20 and an atomic mass close to 40.
How many neutrons does calcium usually have?

• 20

• 18

• 40

• 22

Which element acts like both a metal and a nonmetal?

• Silicon (Si)

• Aluminum (Al)

• Sulfur (S)

• Krypton (Kr)

The smallest unit of matter that retains the properties of an element is called a –

• atom

• cell

• molecule

• nucleus