Unit 1 Introduction to Atoms Quiz Review

What are atoms?

• The smallest unit of chemical compounds

• The basic building blocks of matter

• Large molecules that make up cells

• The components of protons and neutrons

Answer explanation

Atoms are the basic building blocks of matter, meaning they are the fundamental units that make up all substances. The other options describe different concepts related to chemistry and biology, but do not define atoms.

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-5

Which subatomic particle has a positive charge?

• Neutron

• Proton

• Electron

• Isotope

Answer explanation

The proton is the subatomic particle that carries a positive charge, distinguishing it from neutrons, which are neutral, and electrons, which have a negative charge. Isotopes are variants of elements, not particles.

Where are electrons located in an atom?

• Inside the nucleus

• In a cloud around the nucleus

• In the nucleus with protons

• In fixed orbits only

Answer explanation

Electrons are located in a cloud around the nucleus, which reflects their probabilistic nature in quantum mechanics. This contrasts with fixed orbits or being inside the nucleus, where only protons and neutrons reside.

What does the atomic number (Z) represent?

• The total mass of the atom

• The number of neutrons in the nucleus

• The number of protons in the nucleus

• The number of electrons in the atom

Answer explanation

The atomic number (Z) represents the number of protons in the nucleus of an atom. This number determines the element's identity and its position in the periodic table.

Tags

NGSS.MS-PS1-1

How is atomic mass (A) calculated?

• Protons + Electrons

• Protons + Neutrons

• Neutrons - Protons

• Electrons + Neutrons

Answer explanation

Atomic mass (A) is calculated by adding the number of protons and neutrons in an atom's nucleus. Electrons have negligible mass, so they are not included in this calculation. Thus, the correct choice is Protons + Neutrons.

What does a neutral atom indicate?

• More neutrons than protons

• Equal number of protons and electrons

Answer explanation

A neutral atom has an equal number of protons and electrons, which balance each other out, resulting in no overall charge. More neutrons than protons would not affect the charge, making the correct choice the equal number of protons and electrons.

What is an anion?

• A positively charged ion

• A neutral atom

• A negatively charged ion

• A molecule with no charge

Answer explanation

An anion is defined as a negatively charged ion, which means it has gained one or more electrons. This distinguishes it from cations, which are positively charged ions.

What is a cation?

• An atom with equal protons and electrons

• A negatively charged ion

• A positively charged ion

• An atom with no charge

Answer explanation

A cation is defined as a positively charged ion, which means it has more protons than electrons. This distinguishes it from negatively charged ions (anions) and neutral atoms.

What is found at the top of an element's box on the periodic table?

• Element Name

• Atomic Mass

• Atomic Number

• Symbol

Answer explanation

The atomic number, found at the top of an element's box on the periodic table, indicates the number of protons in the nucleus of an atom. It uniquely identifies each element, making it the correct answer.

Which of the following is a correct representation of an element’s symbol?

• oo for Oxygen

• O for oxygen

• o for Oxygen

• O2 for oxygen

Answer explanation

The correct representation of an element's symbol is 'O for oxygen'. Element symbols are typically one or two letters, with the first letter capitalized, making 'O' the accurate symbol for oxygen.