Types of Elements and their Periodic Properties

Question 1

Metals

Answer 1

• Found on the left side and in the middle of the periodic table
  
  • Include active metals, transition metals, lanthanide and actinide series of elements
• Metals are lustrous (shiny) solids
  
  • except mercury which is liquid under standard conditions
• Generally have high melting points and densities
  
  • Exept lithium (density half of water)
• They are malleable (hammered into shapes) and ductile (pulled into wires)
• Low effective nuclear charege, low electronegativity, large atomic radius/small ionic radius, low ionization energy and low electron affinity
• Good conductors of heat and electricity

Question 2

Nonmetals

Answer 2

• Dull, poor conductors of heat/electricity and brittle
• found on the upper, right side of the periodic table
• high ionization energies, electron affinities, and electronegativities and small atomic radii/large ionic radii
• inability to easily give up electrons

Question 3

Metalloids

Answer 3

• also called semimetals
• Posess characteristics of both metals and non metals and are found in a stairstep pattern starting with Boron

Question 4

3 Key rules that control how valence electrons work in an atom

Answer 4

1. moving left to right across a period, electrons and protons are added one at a time.
2. principal quantum number increases by one as you move down the elements in a group
   
   • valence electrons are increasingly separated from the nucleus resulting in reduced electrostatic attraction between the valence electrons and positively charged nucleus
3. elements can gain or lose electrons in order to achieve a stable octet formation of noble (inert) gases “Group VIIIA or Group 18”
   
   • elements, especially those with biological roles, tend to be most stable with eight electrons in their valence shell

Question 5

effective nuclear charge (Z_eff)

Answer 5

• electrostatic attraction between the valence shell electrons and the nucleus
• a measure of the net posotive charge experienced by the outermost electrons
• forms foundation of all periodic trends
• Z_eff increases left to right for elements in the same period with little change in value from top to bottom in a group

Question 6

Atomic Radius

Answer 6

• Refers to the size of a neutral element
• 1/2 the distance between the centers of two atoms of an element that are briefly in contact with one another (similar to diameter calculation)
• decreases from left to right across a period and increases from top to bottom in a group

Question 7

Ionic Radius

Answer 7

• Size of a charged species
  
  • Metals lose electrons and become positive
  • nonmetals gain electrons and become negative
  • Metalloids vary but tend to follow trend based on which side of the metalloid line they fall on
• Largest nonmetallic ionic radii and the smallest metallic ionic radii exist at the metalloid boundary
• Cations are generally smaller than their corresponding neutral atom
• Anions are generally larger than their corresponding neutral atom

Question 8

Ionization Energy (IE)

Answer 8

• aka ionization potential
• energy required to move an electron from the valence shell of a gaseous species
• increases from left to right across a period
• decreases from top to bottom in a group
• endothermic process (requires input of heat)
• The greater greater the Z_eff or closer the valence electrons are to the nucleus, the more difficult it becomes to remove an electron, increasing the IE
• The energy necessary to remove the first electron is called the first ionization energy
• The energy necessary to remove the second electron is called the second ionization energy and so on

Question 9

Active Metals

Answer 9

• Elements in Groups IA and IIA such as lithium and beryllium have such low ionization energies
• they do not exist naturally in their neutral forms
  
  • always found in ionic compounds, minerals or ores

Question 10

Eelctron Affinity

Answer 10

• The amount of energy released when a gaseous species gains an electron in its valence shell
  
  • opposite concept of Ionization Energy
• increases from left to right across a period
• decreases from top to bottom in a group
• Halogens (group VIIA) are the most “greedy” when it comes to electrons. Acquiring 1 additional electron, a halogen is able to complete it’s octet and achieve a noble gas config.
• Exothermic process (expels energy in the form of heat)
• Noble gases have electron affinity of 0 because they already have a stable octet and cannot readily accept an electron

Question 11

Electronegativity

Answer 11

• A measure of the attractive force of the nucleus for electrons within a chemical bond
• Increases from left to right across a period
• decreases from top to bottom in a group
• The greater the electronegativity of an atom, the more it attracts electrons within a bond
• related to ionization energies
  
  • the lower the ionization energy, the lower the electronegativity
  • the higher the ionization energy, the higher the ionization energy
  • The first 3 noble gases are exceptions (high IE but negligible electronegativity because they don’t form bonds)

Question 12

Pauling electronegativity scale

Answer 12

• .7 (Cs) to 4.0 (F)

Question 13

oxidation states (oxidation number)

Answer 13

• charges when forming bonds with other atoms