Periodic Trends and the Elements: Learning and Predicting their Properties

Ch. 6 Periodic Trends Finish learning the Elements and their symbols 1-36, 38 47,50,51,53-56, 78-80, 82, 92

Ch. 6 The Periodic Table Valence Electrons: Electrons found in the last/outer shell of an atom. Past the full inner shells that do not change.

The Octet Rule: Atoms tend to go thru reactions that allow them to gain or lose electrons until they have 8 valence electrons. (Exceptions: H,He, Li, Be, B) lose 1 lose 2 lose 3 gain 4 gain 3 gain 2 gain 1 no change lose 4 +1 +2 +3 +- 4 -3 -2 -1 0

Valence Electrons Elements that gain electrons tend to behave in similar ways Elements that lose electrons tend to behave in similar ways

Development of the Periodic Table KC 1 : They used the properties of the elements to sort them into groups Precursors to the Periodic Table Triads = groups of 3 elements with similar properties Octaves = when ordered by atomic weight, the tendency of atoms to repeat properties every 8th element Dmitri Mendeleev - Russian scientist that organized the elements into a table KC 2: Increasing Atomic Weight (no protons yet) Unfortunately, it doesn’t increase in order

Predicted properties of elements that had yet to be discovered Mendeleev’s Table Ekasilicon: Atomic Wt: 72 Melt Pt: High Density: 5.5 g/mL Color: Gray No Rxn: acid / base Germanium (1886) Atomic Wt: 72.6 Melt Pt: 947C Density: 5.4 g/mL Color: Gray No Rxn: acid / base

Modern Periodic Table KC 3: By the number of protons, or Atomic Number Group: vertical column of the Table, having the same number of valence electrons or e- config - also called families Period: horizontal rows of the Table, show a gradual changing of properties Periodic Law: When elements are arranged in order of increasing Atomic # their properties begin to repeat in a predictable pattern (think Mendeleev)

Modern Periodic Table Periodic Trend: A property that repeats itself in a predictable way when following the Table Group: vertical column of the Table, having the same number of valence electrons or e- config - also called families Period: horizontal rows of the Table, show a gradual changing of properties Periodic Law: When elements are arranged in order of increasing Atomic # their properties begin to repeat in a predictable pattern (think Mendeleev)

Modern Periodic Table Common Periodic Trends: Physical Properties: Density Melting and boiling points Metallic nature Atomic Trends: Electronegativity Atomic radius Ionic size Ionization energy

IUPAC = Intl Union of Pure and Applied Chemistry Groups Numbered 1-18

1A - 8A = this is the grouping we use, it emphasizes valence electrons 1B - 8B/10B = is the “d” block, we won’t use this much

Broad Classes of Elements KC 4: Metals, Non-metals and metalloids or semi- metals Metallic <----> Metalloids <----> Non-Metals Lose electrons Gain electrons Luster (Shiny) not ... Malleable not….. Ductile not….. Conduct Heat not…. Conduct Electricity not…. Mostly Solids Gases Outliers: Mercury, Bromine, Aluminum

Properties of the Group I & II Metals

Section 6.2 KC 10: Names Symbols Atomic # Atomic Wt. Valence (Oxidation States) Electron Configuration Density Melting and boiling point

Section 6.2

KC 11: Representative elements (1-7), Noble Gases (8), Transition Metals (d block), and Inner Transition Metals (f block) Section 6.3 Atomic Radius: essentially the distance from the nucleus to the valence shell KC 16: Increases by the number of Energy Levels as you move down a group, and decreases as you add protons when you move across a period

Atomic Radii

Atomic Radius increases as you move down the Periodic Table because you are adding a new Energy Level Atomic Radius decreases as you move across the Periodic Table from the left to the right because you are adding more protons, thereby strengthening the nuclear positive charge that is pulling inward on the electrons

Ionic Size - change in the size (radius) of an atom when it gains or loses electrons Ion = An atom that has gained or lost an electron and now has a net charge (positive or negative) KC 17 : When at atom gains or loses an electron Cation = A positively charged atom that has lost one or more electrons Anion = A negatively charged atom that has gained one or more electrons

KC 19: If the atom gained electrons then it gets bigger. If the atom loses electrons then it gets smaller. It means the electrons now outnumber the protons, and so the nucleus can’t hold the size of the atom as small, and it gets bigger. Losing electrons is the opposite.

Cation = loses electrons so it decreases in size loses its entire valence shell protons outnumber electrons, “pull” them inward Anion = gains electrons so it increases in size fills valence shell electrons outnumber protons and “loosen” outward

Grey = Neutral Radii, Red = Cationic Radii, Blue = Anionic Radii

Ionization Energy = The energy need to remove an electron (to make a negative charge) KC 18 : Decreases within a group (gets easier to steal an electron as you go down the table) Increases across a period (gets more difficult to steal an electron as they get closer to a full shell) 2nd Ionization Energy - when and why does the spike occur?

Periodic Trends in 1st Ionization Energy

Periodic Trends in 1st Ionization Energy Non-metals, high 1st IE C P I As S Zn Se Si Ga

Beyond 1st Ionization Energy

Electronegativity = An atom’s tendency to gain electrons in a bond/compound. (its greediness for electrons) KC 20 : It increases as you move up a group and it increases as you move to the right across a period Electronegativity would increase as you move across and up the periodic table. You are closer to a full shell, and the electrons are closer to the nucleus in the smaller atoms

Periodic Trends and the Elements: Learning and Predicting their Properties