Unit 2: The Periodic Table and Atoms

Who was Dmitri Mendeleev?

Creator of the version of the periodic table we use today

How is the periodic table organized?

in periods and groups and by increasing atomic number

What does the periodic table of elements look like, what does it consist of?

It has periods and groups, and groups of different types of elements

Alkali metals

• high reactivity, especially with water

• very soft and malleable

• low melting and boiling points

Alkaline Earth Metals

• reactive, but not as reactive as alkali metals

• higher melting points than alkali metals

• metallic luster

• easily conduct heat and electricity

Transition metals

• very good conductor of heat and electricity

• form colorful compounds

• very high melting and boiling points

• often magnetic

Metalloids

• semiconductive

• brittle

• can behave like metals or nonmetals in chemical reactions

Halogens

• non-metal

• high reactivity

• brittle

• solid, liquid, and gas at room temperature

Noble Gasses

• non-reactive

• gas at room temperature

• colorless, odorless, tasteless

Electron configuration

Calcium: 1s² 2s² 2p^6 3s² 3p^6 4s²

Metals

luster, and malleable, and most easily conduct electricity and heat

Metalloids

aren’t as good as a conductor as metals but are better than non-metals and they fall between metals and non-metals in the periodic table

Non-metals

non-metals are very poor conductors of electricity and are brittle if solid

periodic table trends

changes in the periodic table

Atomic radius

• The distance from the nucleus to the outermost shell, or how large the electron energy levels are

• DIFFERENT than the others (decreases across periods, increases down groups)

• Half the distance between the nuclei of two atoms

Ionic Radius

• Similar to atomic radius but gets larger or smaller when the atom becomes an ion

• More electrons = larger ionic radius

• Mg  -2  > Mg

Electronegativity

• An atom’s tendency to attract other electrons

• Increases across periods, decreases down groups

Ionization energy

The amount of energy required to remove an electron from the outermost shell

Anions

negative ions that have gained one or more electrons

Cations

positive ions that have lost one or more electrons

Electron Affinity

the neutral atom’s likelihood of gaining an electron

Timeline of the atom

• Democritus

• Dalton

• JJ Thompson

• Rutherford

• Bohr

• Schrodinger

Dalton’s atomic theory

All matter if made of atoms, atoms of the same element are identical, atoms are combine in more than one ratio, during a chemical reaction atoms can rearrange but cannot but changed or destroyed

Bohr’s atomic model

protons

positive particles in the nucleus (p+)

neutrons

neutral particles in the nucleus (n o)

electrons

negative particles in shells moving around the nucleus (e-)

atomic number

number of protons (same as number of electrons)

atomic mass

number of protons + neutrons

wavelength

• Distance between the identical points, or wave peaks) on successive waves

• Symbol: λ

• Formula: c/f

• Unit: meters

frequency

• The number of complete wave cycles that pass a given point in one second

• Symbol: f

• Unit: Hertz

speed of light

3 × 10^8 m/s

Symbol: c

frequency formula

f= c/λ

wavelength formula

λ=c/f

Energy of atoms

• E = h x f

• h= Planck’s constant (6.63 x 10^-34J x s)

Quantum energy

Quantum energy is the energy in discrete packets called "quanta." It indicates that energy changes happen in specific amounts rather than continuously, like when an electron jumps between energy levels in an atom. This concept helps explain the behavior of particles at the quantum level

small discrete units of energy

Formula for maximum number of electrons in an energy level

• n=1: 2(1²) = 2 electrons

• n=2: 2(2²) = 8 electrons

• n=3: 2(3²) = 18 electrons