TEAS 3.1 Atomic Structure

What is an atom?

the fundamental building block of matter that retains the properties of an element. It is the smallest unit that has a unique identity.

How many known elements are there?

There are 118 known elements arranged in the periodic table.

What are the three subatomic particles that make up all atoms?

Protons, neutrons, and electrons.

What is the nucleus of an atom?

the central core of an atom containing protons and neutrons.

What is the charge and mass of a proton?

a positive charge (+1) and a mass of 1 atomic mass unit (amu).

What is the charge and mass of a neutron?

no charge (0) and a mass of 1 atomic mass unit (amu).

What is the charge and mass of an electron?

a negative charge (-1) and a negligible mass (essentially 0 amu).

Where are electrons located in an atom?

in shells or energy levels around the nucleus, held in place by their attraction to the positive protons.

What is the atomic number?

equals the number of protons in an atom's nucleus. This number defines what element the atom is.

What is atomic mass?

the sum of protons and neutrons in an atom, measured in atomic mass units (amu).

What are isotopes?

atoms of the same element with different numbers of neutrons. They have the same number of protons and electrons but varying atomic masses.

Give an example of isotopes.

Carbon-12 has 6 neutrons, while Carbon-13 has 7 neutrons. Both have 6 protons (making them carbon), but different atomic masses.

What is an ion?

an atom with a positive or negative charge, created when atoms gain or lose electrons.

What is a cation?

a positively charged ion formed when an atom loses electrons, resulting in more protons than electrons.

Give an example of a cation.

Sodium (Na) has 11 protons and 11 electrons. When it loses 1 electron, it becomes Na⁺ with 11 protons and 10 electrons.

What is an anion?

a negatively charged ion formed when an atom gains electrons, resulting in more electrons than protons.

Give an example of an anion.

Chlorine (Cl) has 17 protons and 17 electrons. When it gains 1 electron, it becomes Cl⁻ with 17 protons and 18 electrons.

How is the periodic table organized?

The periodic table arranges elements by increasing atomic number (left to right), groups (vertical columns with similar properties), and periods (horizontal rows indicating outermost electron shell).

What are groups in the periodic table?

vertical columns of elements with similar properties and the same number of valence electrons.

What are periods in the periodic table?

horizontal rows that indicate the outermost electron shell of an atom.

What does the integer shown with each element represent?

the atomic number, which equals the number of protons and the number of electrons in neutral atoms.

What does the decimal number shown for each element represent?

the average atomic mass, accounting for natural isotope abundance.

How many electrons can Period 1 hold?

only an s orbital and can hold a maximum of 2 electrons.

How many electrons can Period 2 hold?

s and p orbitals and can hold a maximum of 8 electrons (s=2, p=6).

How many electrons can Period 3 hold?

has s, p, and d orbitals and can hold a maximum of 18 electrons (s=2, p=6, d=10).

How many electrons can Period 4 hold?

has s, p, d, and f orbitals and can hold a maximum of 32 electrons (s=2, p=6, d=10, f=14).

What are valence electrons?

electrons in the outermost shell that participate in chemical reactions.

What are noble gases and why are they stable?

elements like helium and neon that have full valence shells, making them extremely stable and unreactive (inert). They don't need to gain or lose electrons.

What is the tendency of metals regarding electrons?

Metals (valence < 4) tend to lose electrons, forming positive ions (cations).

What is the tendency of nonmetals regarding electrons?

Nonmetals (valence > 4) tend to gain electrons, forming negative ions (anions).

If nitrogen has 7 protons and 7 electrons, what ion will it form?

it will gain 3 electrons to fill its valence shell, becoming N³⁻ with a -3 charge (7 protons, 10 electrons).

What is an ionic bond?

forms when electrons are transferred from one atom to another, creating oppositely charged ions that attract each other.

What are the properties of ionic compounds?

soluble in water, conduct electricity, and are formed between metals and nonmetals.

Give an example of an ionic bond.

Sodium (Na) loses 1 electron → Na⁺. Chlorine (Cl) gains 1 electron → Cl⁻. The Na⁺ and Cl⁻ attract, forming NaCl (table salt).

What is a covalent bond?

A covalent bond forms when atoms share electrons to achieve stability. These typically form between two nonmetals (p-block elements).

Give an example of a covalent bond.

Two oxygen atoms each have 6 valence electrons. By sharing 2 electrons each (4 electrons total), they form O₂ with a double bond.

How many electrons does it take to make one bond?

It takes 2 electrons to make 1 bond.

What is an orbital?

An orbital is an area around the nucleus where an electron can be found.

How many electrons can an s orbital hold?

a maximum of 2 electrons.

How many electrons can a p orbital hold?

a maximum of 6 electrons.

How many electrons can a d orbital hold?

a maximum of 10 electrons.

How many electrons can an f orbital hold?

a maximum of 14 electrons.

What happens to a carbon atom with 6 protons and 6 neutrons in terms of atomic mass?

A carbon atom with 6 protons and 6 neutrons has an atomic mass of 12 amu.

Why don't electrons significantly contribute to atomic mass?

Electrons are so small that their mass doesn't significantly contribute to the overall mass of the atom.

In a neutral atom, what is the relationship between protons and electrons?

the number of protons equals the number of electrons.

What charge does a carbon atom with 6 protons and 6 electrons have?

has a charge of 0 (neutral) because the positive and negative charges balance out.

Why are atoms most likely to gain or lose electrons?

they are most likely to gain or lose electrons to achieve stability by obtaining a full valence shell.

What is a compound?

a substance made of two or more elements.