Atoms & Elements

What is Kinetic Molecular Theory (KMT) about?

All matter is made of tiny particles that are constantly moving, with space between them.

How does heat affect particles according to KMT?

Adding energy (heat) makes particles move faster and usually increases the space between them.

What are the three states of matter?

Solid, Liquid, Gas.

How do particles in a liquid compare to a solid?

Liquid particles are farther apart and move around more than solid particles.

What is a chemical property?

A property that describes how a substance reacts with another substance to form a new one.

What is a physical property?

A property that can be observed or noticed without changing the substance's identity.

What is a qualitative physical property?

A property that can be described or observed, like color or texture.

What is a quantitative physical property?

A property that can be measured in units, like mass or density.

What are 3 signs a chemical change has probably occurred?

Heat is produced/absorbed, a new color appears or the original color disappears, or gas bubbles/solid chunks form.

What stays the same in a physical change?

The material involved is structurally the same before and after the change.

Name 3 examples of physical changes.

Cutting, Dissolving, Melting.

What are elements made of?

Each element is made up of its own unique type of atom.

What is the atomic number?

It's the number of protons in an atom's nucleus, which is also the number of electrons in a neutral atom.

How many elements are currently known?

118

What is the rule for writing element symbols?

The first letter (or only letter) is always capitalized, which may be followed by 0-2 lowercase letters.

What does a chemical formula show?

It represents a compound and shows which elements are bonded together and how many atoms of each are present.

What is atomic mass?

The total number of protons and neutrons in an atom's nucleus, often expressed in amu.

Name 3 properties of metals.

Good conductors of heat and electricity, shiny, and ductile (can be stretched into wires).

What are non-metals generally like?

Poor conductors of heat and electricity, not ductile or malleable, and often dull in appearance.

What are metalloids?

Substances with properties of both metals and non-metals, like being semiconductors.

What are the vertical columns on the periodic table called?

Groups or Families.

What do elements in the same group/family have in common?

They have similar (but not identical) chemical properties.

What are the horizontal rows on the periodic table called?

Periods.

What does an element's period number tell you?

It tells you the number of principal electron shells (orbits) its atoms have.

What is a proton?

A positively charged subatomic particle found in the nucleus.

What is a neutron?

A neutrally charged (no charge) subatomic particle found in the nucleus.

What is an electron?

A negatively charged subatomic particle that orbits the nucleus.

What was Dalton's model of the atom?

A tiny, indivisible sphere.

What was Thompson's model of the atom nicknamed?

The "plum pudding model".

In Bohr's model, how many electrons can the first orbit hold?

A maximum of 2 electrons.

In Bohr's model, how many electrons can orbits beyond the first hold?

A maximum of 8 electrons.

What do Lewis diagrams show?

Only the valence (outermost) electrons of an atom.

What is an ion?

An atom or molecule with a net electric charge.

What is an ionic bond?

A bond formed when one atom gives up one or more electrons to another atom.

What is a covalent bond?

A bond that involves the sharing of electron pairs between atoms.

What is the "octet" in chemistry?

An outer shell electron configuration of 8 electrons, which atoms try to attain for stability.

What is a cation?

A positively charged ion. (Often formed when metals lose electrons)

What is an anion?

A negatively charged ion. (Often formed when non-metals gain electrons)

Why do atoms lose or gain electrons to form ions?

To achieve a full outer orbit and become stable (follow the octet rule).