3. Atoms and chemistry (2nd exam)

What are atoms?

the basic units of matter

What is an electron’s charge, and where is it located in an atom?

negative, outside the nucleus

What is a proton’s charge, and where is it located in an atom?

positive, inside the nucleus

What is a neutron’s charge, and where is it located in an atom?

no charge, inside the nucleus

As the energy levels get further from the nucleus on the bohr model…

they have more energy

Which particle determines the element?

proton= atomic number

What are ions?

charged atoms

What’s a cation?

When an atom loses electrons, then it loses negative charges and becomes a positive ion. has more protons than electrons (net positive charge)

What’s an anion?

When an atom gains electrons, then it gains negative charges and becomes a negative ion. has more electrons then protons (net negative charge)

What’s an isotope?

An atom of an element with the same number of protons but a different number of neutrons.

How do we find the number of neutrons in an element?

Find the atomic mass- the atomic number

What do the periods (rows) on the periodic table tell us?

The energy levels

What do the groups (columns) on the periodic table tell us?

The number of valence electrons

What’s electronegativity

Measure of attraction of an atom for an electron

What’s the octet rule?

atoms tend to change so that each atom, by gaining, losing, or sharing electrons, has eight electrons in its valence shell.

How do ionic bonds form?

because of the transfer of electrons from the metal to the nonmetal. Metals become positive (cations) and nonmetals become negative (anions)

What’s the law of definite proportions

a given chemical compound always contains the same elements in the exact same proportions by mass

When does metallic bonding form?

Formed between two or more cations (metals)

When are covalent bonds formed?

Covalent bonds are formed between two or more nonmetals

• tend to form gases and liquids more frequently than solids

What’s an acid?

a solution that has an excess of H+ ions.

• tastes sour

• conducts electricity

• break down certain substances

• turn blue litmus paper red

• some acids react with metals

What’s a base?

a solution that has an excess of OH- ions.

• slippery

• taste bitter

• can break down certain substances

• conduct electricity

• turn red litmus paper blue

• dont react with metals

What’s a pH scale?

a measure of how acidic or basic a solution is.

• acidic solutions= below 7, 0= very acidic

• pH 7= neutral

• basic solutions= above 7

The change of one pH unit means what?

it’s not twice as acidic, it’s 10 times more

What’s neutralization?

A reaction between an acid and a base

What are indicators?

Chemicals which change colors when they are put into acids or bases