Matter can exist as which of the following?

What is an element? Fill in the blank: An ______ is a substance that cannot be broken down into another substance by ordinary chemical means.

How many naturally occurring elements are there?

Which four elements make up about 96% of the body weight of most living organisms?

What is the atomic symbol for hydrogen?

Which of the following subatomic elements has no electrical charge and is found in the nucleus?

Protons have a _______ charge and are found in the _______.

Electrons have a negative charge and are found _______ the nucleus moving in orbitals.

The mass number is equal to the sum of which two subatomic particles?

Electrons have about zero mass.

Atomic weight changes with _______.

In a helium atom, protons and neutrons are located ______ the nucleus, while electrons are located ______ the nucleus.

Fill in the blank: All atoms of an element have the same number of _______.

Fill in the blank: The atomic number also gives the number of _______ if an atom is electrically neutral.

The atomic number of Oxygen is ___

What are isotopes?

Isotopes have the same number of _______ but a different number of _______.

What may happen to unstable isotopes?

List one use of radioactive isotopes mentioned in the passage.

Arrangement of Electrons in an Atom: Electrons are constantly _______.

What is useful to construct models of atoms with energy levels or electron shells?

Arrangement of Electrons in an Atom: Each shell contains a certain number of _______.

For atoms up through number 20, how many electrons fill the first shell?

For atoms up through number 20, how many electrons fill each additional shell?

What is the valence shell in an atom? (Fill in the blank: The valence shell is the ________ shell.)

Atoms can give up, accept, or share electrons to have ________ electrons.

Chemical properties of atoms are largely determined by the arrangement of their electrons.

Refer to the diagram of atoms of six important elements. What is the atomic number of Carbon?

Refer to the diagram of atoms of six important elements. Which element has the symbol 'O'?

Refer to the diagram of atoms of six important elements. Fill in the blank: The atomic mass of Sulfur is ___.

Refer to the diagram of atoms of six important elements. Which element has only one electron shell?

Refer to the diagram of atoms of six important elements. Fill in the blank: The symbol for Phosphorus is ___.

What is a molecule?

Which of the following is an example of a molecule? Choose all that apply.

What is a compound?

Which of the following are examples of compounds? Choose all that apply.

Fill in the blank: An ionic bond is the ______ between opposite charges.

Fill in the blank: A covalent bond involves ______ electrons to complete the outer shell.

What type of bond forms when two atoms are held together by the attraction between opposite charges?

How many electrons does sodium have in its valence shell?

What does sodium usually do with its valence electron?

How many electrons does chlorine have in its valence shell?

What does chlorine usually do when forming an ionic bond?

What is an ion?

When sodium becomes an ion, it has one more ______ than electrons: now Na⁺.

When chlorine becomes an ion, it has one more ______ than protons: now Cl⁻.

Ionic compounds are often called ______.

Refer to the diagram 'Formation of Sodium Chloride'. What happens when a sodium atom (Na) reacts with a chlorine atom (Cl)?

Refer to the diagram 'Formation of Sodium Chloride'. Fill in the blank: When sodium loses an electron, it becomes a ______ ion, and when chlorine gains an electron, it becomes a ______ ion.

Refer to the diagram 'Formation of Sodium Chloride'. Which of the following best describes the structure of sodium chloride (NaCl) as shown in the image?

What is covalent bonding?

In covalent bonding, two hydrogen atoms can share electrons to fill their outer shell by overlapping orbitals.

What does the straight line between the two H atoms represent?

What does the molecular formula H2 indicate?

Double covalent bonding: Two atoms share how many electrons?

What type of bond is shown in the diagram of oxygen gas (O2)?

Refer to Figure 2.8 Shapes of Covalently Bonded Molecules. Which model shows the arrangement of electrons in covalent bonds?

What is the bond angle shown in the ball-and-stick model of methane (CH4)?

In the structural model of methane, how many hydrogen atoms are bonded to the central carbon atom?

Refer to Figure 2.8 Shapes of Covalently Bonded Molecules. Which element is at the center of all the models shown?

Which model best represents the actual space occupied by the atoms in a methane molecule?