Chemistry Unit 2 Review

Dmitri Mendeleev

father of the periodic table

• Organized elements by atomic mass

• Predicted unknown elements location and properties accurately

• Not all elements were accurately arranged by mass

Henry Moseley

organized the periodic table based on increasing atomic number.

The Periodic Law

 When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties. 

Metals

Luster (shiny), good conductor of heat & electricity, malleable (hammer into thin sheets), ductile (draw into wire). Found in the left and center of the PT.

Metalloids

not lustrous, semiconductor. Found on the stair step line.

Nonmetals

brittle, poor conductor. Found in the right side of the PT except for H.

Alkali Metals

Soft enough to cut with a butter knife

Shiny 

Very reactive 

1 valence electron

Form +1 charge 

Found in group 1 except for H

Alkaline Earth Metals

Slightly less reactive than group 1 

2 Valence electrons 

Form +2 charge

Found in group 2

Transition Metals

Fairly unreactive

Malleable (Hammered into sheets)  

High Melting & boiling points

Conduct heat & electricity 

Can have multiple charges

Found in the center of the PT (Groups 3-12)

Halogens

Most reactive nonmetals

Love to react with Alkali Metals 

7 Valence Electrons 

Form -1 Charge

Found in group 17

Noble Gases 

Unreactive 

Full valence electrons

All Gas at room temp 

Zero charge (neutral)

Found in group 18

Lanthanides 

Very reactive 

Silvery white metals, tarnish when exposed to air 

Found in atomic numbers 57-71

Actinides  

All radioactive 

Elements are so similar, it is hard to separate 

Found in atomic numbers 89-103

An element’s physical and chemical properties are due to what?

Its electron configuration

The periodic table is arranged so that?

electron configurations can be predicted

Elements in the same period would have the same?

core electron configuration.

Elements in the same group would have the same?

valence electron configuration

Periodic Table can be used as a model to?

Predict the electron configuration of any element based on its location.

Coulomb’s Law -

 The strength of the force between two charged particles depends on the charge of the particles and the distance between them.

• More charge = more force of attraction

• More distance = less force of attraction

The Shielding Effect

Valence electrons are repelled by the core electrons but attracted by the nucleus.

Ion

charged atom caused by the loss or gain of electrons

Anion

• A Negative Ion

  • forms when an atom gains an electron

  • Bigger than neutral atoms

Cation

• A Positive Ion 

  • forms when an atom loses an electron

  • smaller than neutral atoms

Octet Rule

Atoms tend to gain, lose, or share electrons until they have 8 electrons in their outermost (valence) shell, making them stable like a noble gas.

Atomic radius

The measurement from the atomic nucleus to the valence electrons

• Gets bigger right to left and top to bottom

• More protons = more pull = more radius

Ionization energy

the amount of energy required to remove an electron to become a cation 

• Easier to lose electron = less ionization energy

• Gets smaller right to left and bottom to top

Electron affinity

the energy change that happens when an atom gains an electron

• Gets bigger left to right, bottom to top

Electronegativity

 the atom's ability to attract electrons, It’s like an atom tug of war.

• Gets bigger left to right and top to bottom

• Noble gases have 0 electronegativity cuz valance shell is full