Periodic Table of the Elements: Practice

ProblemsGroup and Period

PTE Group• The columns on the PTE are called groups.• Each group follows a pattern.• All the elements in a group have the same number of valence electrons.• All the elements in a group need to gain/lose/share the same number of

valence electrons to achieve ideal electron configuration.• Group number (1-8) indicates the number of valence electrons.

• Group 1=1 valence electron• Group 4=4 valence electrons

• To achieve ideal electron configuration, an element will gain/lose electrons to achieve the number of electrons of the “nearest” Nobel Gas.

Valence Electron Problem 1:• How many valence electrons does Silicon (Si) have?• It is in group 4/14, so it has 4 valence electrons.

Valence Electron Problem 2:• How many valence electrons does Barium (Ba) have?• It is in group 2, so it has 2 valence electrons.

Valence Electron Problem 3:• How many valence electrons does Iodine (I)have?• It is in group (7/17), so it has 7 valence electrons.

Ideal Electron Configuration Problem 1:• How must the number of electrons change for Nitrogen (N) to be

stable?• Nitrogen is in Period 5/15.• It is three “spaces” away from Neon, the nearest Noble Gas.• It is five spaces away from Helium, the next closest Noble Gas.• It can either gain 3 electrons or lose 5 electrons to get an ideal electron

configuration.• It is more likely it will gain 3 electrons.

Ideal Electron Configuration Problem 3:• How must the number of electrons change for Carbon (C) to be

stable?• Carbon is in Period 4/14.• It is four “spaces” away from Neon, the nearest Noble Gas.• It is four spaces away from Helium, the next closest Noble Gas.• It can either lose 4 electrons or gain 4 electrons to get an ideal electron

configuration.• It is equally likely that it will gain or lose 4 electrons.

Ideal Electron Configuration Problem 3:• How must the number of electrons change for Sulfur (S) to be stable?• Sulfur is in Period 6/16.• It is two “spaces” away from Argon, the nearest Noble Gas.• It is six spaces away from Neon, the next closest Noble Gas.• It can either lose 6 electrons or gain 2 electrons to get an ideal electron

configuration.• It is more likely it will gain 2 electrons.

Electron Configuration and Electron Shells• As electrons get added, they start filling in available spaces in each

Electron Shell.• There are 7 known electron shells, each containing several orbitals that

can hold electrons.• When a shell is the valence (outer) shell, it will never hold more than 8

electrons.• The number of electrons in each shell are sometimes indicated on the

PTE.• The period (row) that an element is found in indicates which shell is the

valence shell.

Electron Shell Problem 1• How many electron shells does Tin (Sn) have?• It is in period 5, so it has 5 shells, the first 4 of which are full.

Electron Shell Problem 2• How many electron shells does Silicon (Si) have?

• It is in period 3, so it has 3 shells, the first 2 of which are full.

Electron Shell Problem 3• How many electron shells does Copper (Cu) have?• It is in period 4, so it has 4 shells, the first 3 of which are full.

Valence Shells and Electrons Problem 1:• An element has 3 valence electrons and 3 electron shells. What

element is it?• If it has 3 valence electrons, it is probably from group 3/13.• If it has 3 electron shells, it must be period 3.• The matching element is Aluminum.

Valence Shells and Electrons Problem 2:• An element has 7 valence electrons and 2 electron shells. What

element is it?• If it has 7 valence electrons, it is from group 7/17.• If it has 2 electron shells, it must be period 2.• The matching element is Fluorine (F).

Valence Shells and Electrons Problem 3:• An element has 5 valence electrons and 5 electron shells. What

element is it?• If it has 5 valence electrons, it is from group 5/15.• If it has 5 electron shells, it must be period 5.• The matching element is Antimony (Sb).

Simple Problem 1:• An element is in group 6/16 and period 4. What element is it?• The matching element is Selenium (Se).

Simple Problem 2:• An element is in group 3/13 and period 7. What element is it?• Ununtrium

Simple Problem 3:• How many electron shells and valence electrons does the element

Strontium (Sr) have?• It is in period 5, so it has 5 electron shells.• It is in group 2, so it has 2 valence electrons in its valence shell.

Tough Problem 1:• An element has 12 neutrons in a typical isotope, and has an ideal

electron configuration identical to neon. What element is it?• If its ideal electron configuration is the same as neon’s, it must be within 4

spaces of neon.• Fluorine is not massive enough: it only has 10 neutrons.• Looking at more massive elements, sodium has a mass of 23 and an atomic

number of 11. 23-11=12 neutrons. Sodium matches.• Magnesium has a mass of 24 and 12 protons. 24-12=12 neutrons.

Magnesium matches.

Tough Problem 2:• An element needs to gain or lose 2 electrons to gain ideal electron

configuration. It has 5 filled electron shells, and one partially filled shell. What elements could it be? • It must be in period 6.• Barium could lose 2 electrons to become like Xenon, or Polonium could gain 2

electrons to become like Radon.

Tough Problem 3• An element has 81 neutrons, and an ideal electron configuration

similar to Xenon. What element is it?• It must be in period 5 or 6.• Barium has an atomic mass of 137, and 56 protons. 137-56=81 neutrons.• Barium must be the answer.