PAGE 1 — Basic Atomic Structure & PAGE 2 — Electrons, Shells, Ions

What is an atom?

The smallest unit of matter that still has the properties of an element.

Atoms form bonds when they?

• Gain electrons

• lose electrons

• share electrons

What are chemical bonds?

The attraction that holds atoms together

• the pull between electrons and neutrons

Where are protons and neutrons located?

In the nucleus of the atom.

Where are electrons located?

In electron shells/orbitals around the nucleus.

What is the charge of a proton?

+1 (positive)

What is the charge of a neutron?

0 (neutral)

What is the charge of an electron?

–1 (negative)

What determines the atomic number?

The number of protons

What determines the mass number?

Protons + neutrons

Which particle changes when an atom becomes an ion?

Electrons (gained or lost)

Which particle changes when an atom becomes an isotope?

Neutrons

What makes an atom neutral?

Protons = electrons

What is the smallest unit of matter?

Atom

What is a positive particle; determines element?

Proton

What is a neutral particle; changes mass?

Neutron

What is negative particle; affects charge?

Electron

What is an atom with charge (electrons change)?

Ion

What is the atomic number?

The number of protons in an atom.

What does the atomic number determine?

The identity of the element.

Which particle is not included in the mass number?

Electrons

What changes when the mass number changes?

The atom becomes an isotope.

What changes when the atomic number changes?

The element changes.

What is an isotope?

Atoms of the same element with different numbers of neutrons.

What stays the same in all isotopes?

The number of protons (atomic number)

What changes in isotopes?

The number of neutrons, which changes the mass number.

Do isotopes have the same chemical properties?

Yes, because they have the same number of electrons.

What is an ion?

An atom that has gained or lost electrons and now has a charge.

What particle changes when an ion forms?

Electrons (never protons)

What is a cation?

A positively charged ion.

How does a cation form?

By losing electrons.

What is an anion?

A negatively charged ion.

How does an anion form?

By gaining electrons.

Do protons ever change when forming ions?

No

• changing protons changes the element.

Why do metals form cations?

They lose electrons easily.

Why do nonmetals form anions?

They gain electrons easily.

What are electron shells?

Energy levels around the nucleus where electrons are found.

Where are electrons located?

In shells/orbitals surrounding the nucleus.

Which electrons determine bonding?

Valence electrons (outermost shell).

How many electrons can the first/K shell hold?

2

How many electrons can the second/L shell hold?

8

How many electrons can the third/M shell hold?

18

How many electrons can the fourth/N shell hold?

32

What happens when the valence shell is full?

The atom is stable and unlikely to react.

Why do atoms form bonds?

To fill their valence shell and become stable.

What particle moves during chemical bonding?

Electrons (never protons or neutrons).

What is the region within a shell where electrons are found?

Orbital

A reactive atom has an?

Incomplete valence shell

What is relative atomic mass?

The weighted average mass of all naturally occurring isotopes of an element.

Why is relative atomic mass usually a decimal?

Because it averages multiple isotopes, not just one.

What are valence electrons?

The electrons in the outermost shell of an atom.

Why are valence electrons important?

They determine bonding and chemical reactivity.

What happens when an atom has a full valence shell?

It is stable and not reactive.

How many valence electrons do most atoms want?

8 (the octet rule), except hydrogen and helium (want 2).

What do metals do with valence electrons?

Lose them to form cations.

What do nonmetals do with valence electrons?

Gain or share them to form anions or covalent bonds.

What determines an element’s group on the periodic table?

The number of valence electrons.

What is the octet rule?

Atoms want 8 valence electrons for stability.

A group of atoms that all have the exact same number of protons is called an?

Element

Electrons determine?

How atoms interact with one another and decide if the atom as a whole is positive, negative, or neutral.

Energy levels of an atom refers too?

The amount of valence shells/rings an atom has

Atomic Radius increases as?

Energy levels are added

• makes shell bigger

Atomic Radius decreases as?

More protons are added

• attracts electrons to come closer, make shell smaller

The farther away from the nucleus an electron is?

The more energy it has

Chemical bonds involve a?

Negative-positive reactions between electrons and nucleus

Electrons shells always fill?

Their inner most layer first

• inner → outer

What is a polar bond?

A covalent bond with a separation of charge

• One atom pulls electrons harder

• That side becomes slightly negative

• The other side becomes slightly positive