Properties of Materials: Atomic Structure, Periodic Table, and Chemical Bonding

Practice questions covering atomic structure, trends in the Periodic Table (Groups 1, 7, and 8), and the formation of ionic and covalent bonds.

What does the atomic number of an element represent?

The number of protons contained in the atom.

What information does the mass number provide?

The total number of protons and neutrons in an atom.

Which subatomic particles have a positive charge, a negative charge, and no charge respectively?

Protons have a positive charge, electrons have a negative charge, and neutrons have no charge.

Why does an atom have no overall electrical charge?

The number of protons is the same as the number of electrons, so the positive and negative charges balance out.

In the example of Lithium (Atomic number $3$, Mass number $7$), how many neutrons are present?

There are $4$ neutrons ($7-3=4$).

What is the definition of density?

The measure of the mass for a fixed volume of a substance, usually given in $g/cm^3$.

Which scientist developed the model where electrons move in different electron shells or energy levels?

Niels Bohr.

What is the maximum number of electrons that can fit in the first, second, and third electron shells?

The first shell holds up to $2$ electrons, while the second and third shells each hold up to $8$ electrons.

What forces hold electrons in place within their shells?

Electrostatic forces.

What is the electronic arrangement for a boron atom, which contains five electrons?

$$2,3$$

What is the common name for the elements in Group 1 of the Periodic Table?

Alkali metals.

What happens to the melting points of Group 1 elements as you move down the group?

The melting points decrease as you move down the group.

How does the reactivity of Group 1 metals with water change as you go down the group?

The reactivity increases as you go down the group.

What similarity is found in the electronic structure of all Group 1 elements?

They all have one electron in their outermost electron shell.

What is the common name for the elements in Group 7 of the Periodic Table?

Halogens.

What happens to the boiling points of Group 7 elements as you move down the group?

The boiling points increase as you move down the group.

What is the common name for the elements in Group 8 of the Periodic Table?

Noble gases.

Why are noble gases inert (unreactive)?

They have full outermost electron shells, making them stable.

How is an ion formed?

An ion is formed when an atom loses or gains electrons to achieve a full outermost electron shell.

What is the charge of a sodium ion, and why?

A sodium ion has a charge of $+1$ (written as $Na^+$) because it loses one negatively charged electron, leaving it with more protons than electrons.

What is an ionic bond?

A chemical bond formed by the attraction between a positively charged ion and a negatively charged ion.

Why is potassium more reactive than lithium?

Potassium's outermost electron is further from the nucleus, meaning the electrostatic forces are weaker and the electron is lost more easily.

What is a covalent bond?

A chemical bond where atoms share a pair of electrons to fill their outermost electron shells.

How is a molecule defined?

A group of atoms held together by covalent bonds.

What is a dot and cross diagram?

A diagram used to show how electrons are shared or transferred in chemical bonds, where dots represent electrons from one atom and crosses represent electrons from another.

What is the chemical formula for ammonia?

$$NH_3$$

What is the chemical formula for methane?

$$CH_4$$

What type of bond forms between a metal and a non-metal?

An ionic bond.

What type of bond forms when two non-metals react?

A covalent bond.