Periodic Table and Trends

Organization of the Periodic Table1. First created by Dmitri

MendeleevA. Organized atoms by

atomic masses

B. This was ok, but trends in the periodic table did not match up

A. Mendeleev was able to predict how elements interacted with each other and wanted his table to display those trends.

Henry Moseley

1. Took the nuclear charge, which is the number of protons in the nucleus, and ordered the periodic table using the number of protons in the atom.

2. The trends found by Mendeleev were in place.

Periodic Law

1. States that physical and chemical properties of elements are properties of their atomic number.

2. Each column on the periodic table is called a group

A. Groups have the same number of electrons in their outer-most sublevel

3. Each row in the periodic table is called a period

4. Elements in the same period share the same energy level.

Noble Gases

Noble Gases

1. Group 8A

2. Have filled s and p orbitals

3. Are very stable. Do not form bonds with other molecules

4. All atoms desire to be noble gases and will give or take electrons from other atoms to do so.

A. This is how a compound/molecule is made

5. To act like noble gases, atoms will take the easiest route, and either give up electrons or gain them

Alkali Metals

Alkali Metals

1. Found in Group 1A

2. Made of soft metals (meaning easy to bend)

3. Outer electron shell has an s1 configuration

4. React quickly with water or airA. Can create a basic solution with water

5. Have an extra electron to give up in order to form a +1 ion.

[why is it +1? If you look at Li, Li has 3 protons, so it must have 3 electrons. To get to the nearest noble gas, helium, Li would have to lose 1 electron.

Alkaline Earth Metals

Alkaline Earth Metals

1. Group 2A

2. Outershell has a s2 configuration

3. Metals are harder and less reactive

4. Become ions with a +2 charge

Transition Metals

Transition metals

1. Groups 3B-12B

2. Harder metals and even less reactive than groups 1 and 2

Lanthanides

Lanthanides

1. Contain atomic numbers 57-71

2. Shiny and reactive metals

3. Some glow when electrons hit them.

[europium]

4. 4f series

Actinides

Actinides

1. 5f series

2. All are radioactiveA. Uranium important for nuclear reactions

B. Many are man-made

Main Block Elements

1. Groups 3A-8A

2. Made of metals, metalloids, and nonmetalsA. Metal examples: aluminum, gallium, indium, tin

thallium, lead, bismuth, polonium

B. Metalloids: boron, silicon, germanium, arsenic, antimony, and tellurium.

C. Nonmetal examples: hydrogen, oxygen, nitrogen, carbon, phosphorus, sulfur, selenium, fluoride, chlorine, bromide, iodine, and noble gases

3. The periodic stair step: The area on the periodic table that divides the metals from the nonmetals

A. Atoms around the stair step are metalloidsi. Metalloids have characteristics of nonmetals and

metals

ii. Metalloids are also termed semiconductors

Halogens

Halogens

1. Group 7A

2. Form salts with group 1 metals

3. The most reactive nonmetals

4. Gain electrons to have a noble gas configuration

A. Become a -1 ion if this happens

Chalcogens

1. Group 6A

2. Try to gain two electrons to have a noble gas electron configuration.

A. Become a -2 ion if this happens

Periodic Trends

1. The four different trends to know include:A. Electronegativity

B. Atomic radius

C. Electron affinity

D. Ionization energy

Electronegativity

1. Defined by an atoms tendency to attract electrons in a chemical bond.

2. In a chemical bond, atoms have to share electrons

3. The atom with a higher electronegativity will keep the electrons closer to it.

4. Atoms with the highest electronegativity are found in the upper, right-side of the periodic table; excluding noble gases.

5. The atom with the highest electronegativity is fluorine

A. The lowest is francium

Atomic Radius

1. Atoms with the largest atomic radius are found at the bottom, left-side of the periodic table

why?

2. The further you go down the periodic table, the more energy levels an atom contains.

A. This means, assuming the atom looks like a sphere, the radius of the atom would increase as you go down the periodic table.

3. The top, right-area of the periodic table has the smallest atomic radius (helium)

4. Which would you assume to have the largest atomic radius: Al, Al+, or Al-

5. Which would you assume to have the smallest atomic radius: C2+, C+, C, C-, C2-

Ranking Elements by Atomic Size

PLAN:

SOLUTION:

PROBLEM: Using only the periodic table, rank each set of main group elements in order of decreasing atomic size:

(a) Ca, Mg, Sr (b) K, Ga, Ca (c) Br, Rb, Kr (d) Sr, Ca, Rb

Elements in the same group increase in size as you go down; elements decrease in size as you go across a period.

(a) Sr > Ca > Mg These elements are in Group 2A(2), and size decreases up the group.

(b) K > Ca > Ga These elements are in Period 4, and size decreases across a period.

(c) Rb > Br > Kr Rb has a higher energy level and is far to the left. Br is to the left of Kr in Period 4.

(d) Rb > Sr > Ca Ca is one energy level smaller than Rb and Sr. Rb is to the left of Sr in the same period.

Ionization Energy

1. Defined as the energy needed to remove an electron from an atom

2. The top, right-area of the periodic table contains the atoms with the highest ionization energy.

3. Helium has the highest ionization energy.

Ranking Elements by First Ionization Energy

PLAN:

SOLUTION:

PROBLEM: Using the periodic table only, rank the elements in each of the following sets in order of decreasing IE1:

(a) Kr, He, Ar (b) Sb, Te, Sn (c) K, Ca, Rb (d) I, Xe, Cs

IE decreases as you proceed down in a group; IE increases as you go across a period.

(a) He > Ar > Kr

(b) Te > Sb > Sn

(c) Ca > K > Rb

(d) Xe > I > Cs

These three elements are all in Group 8A(18), IE decreases down a group.

These are all in Period 5, IE increases across a period.

Ca is to the right of K; Rb is below K.

I is to the left of Xe; Cs is further to the left and down one period.

Electron Affinity

1. The ability of an atom to attract and hold onto an atom.

2. Electron affinity is highest in the upper, right-area of the periodic table.

3. Fluorine has the highest electron affinity.

4. Shielding effect: inner electrons are shielding the pull of the nucleus, so outer electrons are removed before inner electrons.

A. That is why Francium is so reactive. It quickly reacts with something around it.

B. Electrons in the outer energy levels feel less of the nuclear charge (they feel less of the positive charge).