Units 2.4-2.6, Chemistry

Atoms are made of:

Subatomic particles called electrons, neutrons, and protons

Nucleus of an Atom

The center of the atom that contains 99.9% of its mass, is made of protons and neutrons, and is positively charged

Electrons

Negatively charged and are found in electron clouds/shells around the nucleus

AMU

Atomic mass unit, equvilent to g/mol

Atomic Number

Number of protons in an element

Atomic Mass

Atomic Number + Number of Neutrons

What happens to electrons during chemical reactions?

They are added or taken away

Ions

Charged atoms

Electrons on the outer most shell

Valence electrons

Cations

Positively charged ions after losing electrons

Anions

Negatively charged ions after gaining electrons

Isotopes

Atoms of the same element but with a different number of neutrons

Radioisotopes

Unstable isotopes that go through a radioactive reaction to make a stable nucleus

Radioactivity

The ability of a substance to emit high energy radiation

Alpha Particle

+2 charge, 4 amu, α symbol

Beta Particle

-1 charge, 0 amu, β symbol

Gamma

0 charge, 0 amu, γ symbol

Amu of an isotope

whole number

Amu of an element on the periodic table

average of all isotopes, not a whole number

AMU formula

% of mass of isotope A + % of mass of isotope B

Groups/Families

Columns on periodic table that are sorted by having the same chemical properties

Periods

Rows on periodic table

Periodic Law

Elements are arranged in order of increasing atomic number

Element in “A” group

Representative elements

Elements in “B” group

Transition elements

₁¹H

Protium, 1 proton, 0 neutrons

₁²H

Deuterium, 1 proton, 1 neutron

₁³H

Tritium, 1 proton, 2 neutrons

Inner Transition Metals

Bottom two rows on periodic table, period 6 and 7

Metals

Solid at room temp except for Hg, they lost atoms in chem reactions to form cations

Metalloids

Show properties of metals and nonmetals, semiconductors

Nonmetals

Found in all states of matter, gain electrons in chemical reaction to form anions

Acid

Compound of H₂ and nonmetals

Alkali Metals

Group 1A except for H, very reactive, never found pure in nature, +1 possible charge

Alkaline Earth Metals

Group 2A, harder, less reactive, only CBS react with water to form basic hydroxides, +2 possible charge

CBS

Calcium (Ca), Barium (Ba), Strontium (Sr)

Halogens

Group 7A, diatomic pure elements, exist in all 3 states of matter, they react with metals for ionic compounds and hydrogen for acids, -1 possible charge

Gas Halogens

F₂ and Cl₂

Solid Halogen

I₂

Liquid Halogen

Br₂

Noble Gasses

Group 8A, don’t react with other chemicals, no charge

Elements that are gasses at room temp

H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, Rn, Uuo

Elements that are liquid at room temp

Hg and Br

Element symbols that don’t match their English name

Fe (Iron), Ag (Silver), Hg (Mercury), Cu (Copper)

Mendeleev’s Periodic Table

Ordered elements by atomic mass, created groups/families, used patterns he saw in similar elements to predict elements discovered in the future