CHEM MIDTERM

What is an atom?

The smallest unit of matter that maintains its chemical identity.

What is the electron configuration for aluminum?

1s²2s²2p⁶3s²3p¹

As atoms bond with each other, they…

Decrease their potential energy, thus creating more-stable arrangements of matter.

If the atoms that share electrons have an unequal attraction for the electrons, the bond is called…

Polar.

An atom is electrically neutral because…

The numbers of protons and electrons are equal.

According to VSEPR theory, what is the shape of CH₄?

Tetrahedral.

What is the formula for calcium oxide?

CaO.

Most of the mass of an atom is occupied by the…

Nucleus.

The total number of protons and neutrons in the nucleus of a single atom is its…

Mass number.

A 'packet' of electromagnetic radiation is called…

Photon.

A line spectrum is produced when an electron moves from one energy level…

To a lower energy level.

The change of an atom from an excited state to the ground state always requires…

Release of energy.

Which of the following orbital notations for phosphorus is correct?

The one with 1s², 2s², 2p⁶, 3s², 3p³.

The atomic number of lithium is 3. What is the atomic number of the next element in the same group?

The atomic number of the next element in the same group, sodium, is 11.

An isotope of chlorine has an atomic number of 17 and a mass number of 35. Which is the correct set of subatomic particles?

17 protons, 17 electrons, and 18 neutrons.

How many atoms are equivalent to 3.5 mol of silicon?

2.1 × 10²⁴ atoms.

Elements to the right side of the periodic table (p-block elements) have properties most associated with…

Nonmetals.

The elements whose electron configurations end with s²p⁶ in the highest occupied energy level belong to Group…

18 (noble gases).

As electrons add to s and p sublevels in the same main energy level, they are pulled closer to the nucleus, causing…

Atomic radii to decrease in size.

What is the correct, balanced equation when rubidium reacts with zinc nitrate?

2Rb + Zn(NO₃)₂ → Zn + 2RbNO₃.

What is a positive ion called?

Cation.

In the three molecules, O₂, HCl, and F₂, which atom would have a partial negative charge?

Chlorine (in HCl).

Which type of reaction is this: 2KClO₃ → 2KCl + 3O₂?

Decomposition.

What are the products of this reaction: CH₄(g) + O₂(g)?

CO₂(g) + H₂O(g).

What does the chemical formula for an ionic compound represent?

The total number of ions in the crystal lattice.

Which group of elements satisfies the octet rule without forming compounds?

Noble gases.

The ions in most ionic compounds are organized into a…

Crystal.

What is the correct, balanced equation when aluminum reacts with oxygen?

4Al + 3O₂ → 2Al₂O₃.

How many electrons must be shown in the Lewis structure of the hydroxide ion, OH⁻?

8 electrons.

In an equation, the symbol for a substance dissolved in water is followed by…

(aq).

What is the term for a neutral group of atoms held together by covalent bonds?

Molecule.

Which coefficients balance this equation: NH₄NO₃ (s) → N₂ (g) + H₂O (l)?

1, 2, 2.

Which statement best describes an element?

A pure substance made up of only one kind of atom.

What is the name of PbSO₄?

Lead (II) sulfate.

Which of the following elements is NOT a metal?

H.

Name the compound KClO₃.

Potassium chlorate.

What is the percent composition of CF₄?

13.6% C; 86.4% F.

In a chemical reaction…

The mass of the reactants equals the mass of the products.

In writing a chemical equation that produces hydrogen gas, which is the correct representation of hydrogen?

H₂.

Of the following molecular formulas for hydrocarbons, which is an empirical formula?

CH₂.

Which is the correct skeleton equation for showing that carbon and oxygen form carbon dioxide?

C (s) + O₂ (g) → CO₂ (g).

A three-dimensional region around a nucleus where an electron may be found is called…

An orbital.

Why does atomic radius increase moving down a group?

The number of occupied energy levels increases.

How does the energy required to remove an electron from an atom change as you move across a period?

It generally increases.

Most of the volume of an atom is occupied by the…

Electrons.

The atomic number of oxygen, 8, indicates that there are eight…

Protons in the nucleus of an oxygen atom.

If electrons in an atom have the lowest possible energies, the atom is in the…

Ground state.

Name the compound SO₃:

Sulfur trioxide.

What is the formula for diphosphorus pentoxide?

P₂O₅.