Periodic Trends (Cov. + Ionic) Test Flashcards
Who published the first classification system?
Dobereiner
What did Dobereiner group the elements into?
Triads
Based off of similar chemical properties
Example of triads
Cl, Br, and I
Dmirtri Mendeleev
Published the first periodic table
arranged the elements in his periodic table in order of increasing atomic mass
Differences between Mendeleev’s table and ours
His was arranged by atomic mass
Ours is arranged by atomic number
HGJ Mosely
The Periodic Law
The Periodic Law
when elements are arranged by increasing atomic number, their physical and chemical properties show a pattern
What is important about the periodic law?
It allows new elements to be discovered
Groups/families
vertical columns on periodic table
Periods
horizontal rows on periodic table
Alkali elements
group 1 elements
the most reactive metals
ALL react with water
silvery in appearance
Alkaline earth metals
group 2
harder, dense, strong
less reactive than alkali, but still too reactive to be in nature
How can you get alkali and alkaline metals?
Extract from compounds
since too reactive to be found in nature
Transition metals
good conductors of electricity
realitively non-reactive
found in nature
harder, denser, than alkali and alkaline
Halogens
group 17
most reactive non-metals
react with metals to form salts
Noble gases
least reactive of all elements
have a complete outer shell of electrons
Octet
complete outer shell of electrons
noble gases have
Metalloid
have properties of metals and non-metals
everything to the left of metalloid staircase is a metal
everything to the right of metalloid staircase is a non-metal
Atomic size
Distance from the nucleus to an atom’s outermost electron
What happens to atomic size as you go across?
It decreases
What happens to atomic size as you go down?
It increases
First ionization energy
the energy required to remove an electron from an atom
What happens to ionization energy as you go across?
It increases
What happens to ionization energy as you go down?
It decreases
Electronegativity
the ability of an atom of an element to attract electrons when the atom is in a compound
What happens to electronegativity as you go across?
It increases
What happens to electronegativity as you go down?
It decreases
The octet rule
atoms want to give, receive, or share electrons to become stable
for most, this means having 8 electrons in outer shell
Ionic bonds
formed through the giving and taking of electrons
Covalent bonds
formed through the sharing of electrons
electrons are not given up completely
Compounds with more than two elements
Ionic
Compounds composed of two non-metals
covalent
Compound composed of a metal and non-metal
ionic
What type of element looses electrons?
Metals always loose electrons to become stable
Metals are always first in the formula
Why type of element gains electrons?
Non-metals
They are second in the formula
What is the charge of a metal in a compound?
Positive
What is the charge of a non-metal in a compound?
Negative
Polyatomic Ions
Molecules that carry a net charge (positive or negative)
When do polar molecules occur?
When there is a net pole
What is a polar molecule?
One side of the molecule is partially negative the otherside is partially positive
How does a molecule become polar?
When one atom has a high electronegativity and then this atom attracts the electrons
creates a distortion of charges
Two things to determine if polar or non-polar?
- Difference in electronegativity
2. Molecule shape
Nonpolar
When atoms in the bond pull equally
Which has a higher boiling point polar or non-polar?
Why?
Polar has a higher boiling point because one end of the molecule is positive and one end is negative. This allows opposites to attract and easily form bonds between molecules. These bonds are strong and are hard to break
