Chemistry Structure 3: Classification of Matter

Which group of metals is group 1 on the ptable? Group 2?

Alkali Metals, Alkaline Earth Metals

What are 6 properties of Alkali Metals?

• Soft solids

• Shiny silvers that dulls in air

• Low melting points

• Good heat/electricity conductors

• Too reactive to be found alone in nature - stored in oil

• Low densities

What are 5 properties of Alkaline Earth metals?

• Malleable, but harder than Alkali metals

• Shiny grey/white silvery that dulls in air

• Melting points higher than Alkali Metals

• Good heat/electricity conductors

• Too reactive to be found alone in nature

What are 5 properties of Transition Metals?

• Hard, but malleable

• Lustrous

• High melting points

• Good heat/electricity conductors

• Low reactivity - can be found in nature

What group of elements is located along the “staircase” starting at Boron of the ptable?

Metalloids

What is the trend in melting points of metals?

Melting point decreases down a group (increased electron shells/atomic radius means less attraction to electrons)

What is the trend in electrical conductivity of metals?

Increases down a group (increased atomic radius/electron shells makes it easier for delocalized electrons to move due to less attraction)

Decreases across a period (increased Z_eff means the opposite effect)

What are 5 properties of metalloids?

• Brittle like non-metals

• Shiny like metals

• Higher melting points than non-metals, but lower than metals

• Semi-conductors: only conduct some heat, not electricity

• Will share electrons in covalent bonds like non-metal

What group of elements is located to the right of the “staircase” of the ptable?

Non-metals

What are 6 properties of Non-metals?

• Most are gases but if solid, are brittle

• Not shiny, dull

• Low melting points

• Bad conductors

• Low reactivity

• Low densities

What group of elements is group 17 on the ptable?

Halogens

What are 5 properties of Halogens?

• Exist in all 3 states of matter (going down the group)

• Are all diatomic elements

• Low melting points

• Poor conductors, if solid (iodine, astatine), are brittle

• High reactivity

What is the color of each Halogen?

Fluorine: Pale yellow

Chlorine: Yellow green

Bromine: Orange Brown

Iodine: Purple

Astatine: Black

What will the color of the solution be if two halogens react?

Will become the color of the halogen that is by itself (not bonded to another element) in the product, aka, the halogen being replaced in the reaction

What is the trend in melting point down the halogen group?

Melting point increases down the group because the state of matter goes from gas to solid, increasing the amount of attraction between particles and making each element harder to melt (more molar mass → more LDFS → more attraction)

What is the trend in reactivity down the halogen group?

Reactivity decreases down the halogen group (decreasing electronegativity)

What group of elements is group 18 on the ptable?

Noble gases

What group of elements is the F-block of the ptable?

Lanthanides/actinides

What are 3 properties of lanthanides and actinides?

• Metals

• Harder and more brittle than transition metals

• Actinides are mostly radioactive so they aren’t found in nature

What is effective nuclear charge (Z_eff)? What is the formula for it?

The attraction between protons in the nucleus and valence electrons, Z_eff = # of protons - # of non-valence electrons

What is the periodic table trend of effective nuclear charge?

Increases across periods, but remains relatively the same down a group

Why does Z_eff remain constant down a group?

Electron shielding increases down a group, which cancels out the increasing nuclear charge down a group so that each element’s EFFECTIVE nuclear charge is around the same (more protons means more nuclear charge, but more electrons means more shielding that cancels it out)

What is electron shielding?

The phenomenon that occurs when inner shell electrons block electron attraction between the nucleus and valence electrons

What is the periodic table trend of electron shielding?

Increases down a group (more electron shells means more electrons between nuclei and valence electrons)

What is atomic radius?

(The distance between 2 nuclei of atoms of the same element)/2

What is the periodic table trend of atomic radius?

Increases down a group (increasing electron shells and shielding)

Decreases across a period (increasing Z_eff attracts electrons and nuclei closer together)

What is ionic radius?

Atomic radius but for ions

How do the sizes of cations and anions differ?

Cations will be smaller than their parent atom (losing electrons)

Anions will be larger than their parent atom (gaining electrons)

What is the periodic table trend of ionic radius?

Increases down a group, decreases across a period

What is First Ionization Energy?

The amount of energy required to remove 1 mol of electrons from 1 mol of gaseous atoms in their ground state

What is the periodic table trend for First ionization energy?

Decreases down a group (increased electron shielding)

Increases across a period (increased Z_eff)

What are exceptions of the First Ionization energy trend?

Groups 13 and 16, because they are more willing to lose electrons to become half or fully filled outer shells

What is Electron Affinity?

The energy change when 1 mole of electrons is added to one mole of gaseous atoms to form one mole of gaseous ions

What is the periodic table trend for Electron Affinity?

Increases across a period (increased means higher attraction, Z_eff more energy released)

Decreases down a group

What is electronegativity?

A measure of how capable an element is of attracting a pair of shared electrons in a covalent bond

What is the periodic table trend for Electronegativity?

Increases across a period (increasing Z_eff)

Decreases down a group (increasing electron shielding)

What will be the products of a reaction between an alkali metal and water?

Hydrogen Gas (H₂) + A Metal Hydroxide, and heat (exothermic reaction)

What will be the products of a reaction between an alkali metal and a halogen?

Ionic halides and heat (exothermic reaction)

What will be the products of a reaction between an alkali metal and an acid?

Hydrogen Gas (H₂) + A salt

What will be the products of a reaction between an silver nitrate and a halogen?

Silver halide

What are silver halides?

Solid precipitates that form after the nitrate ion in silver nitrate is displaced by a halogen

What is silver nitrate used to test?

Tests if there are halogens in a solution because silver nitrate is colorless but turns cloudy when reacting with a halogen

What are Displacement Reactions?

The relative reactivity of elements seen by placing them in direct competition for an extra electron

List the Period 3 oxides in order from most acidic to most alkaline of the solutions that they will form when reacting with water. Which of these oxides are amphoteric?

Na₂O, MgO, Al₂O₃, SiO₂, P₄O₁₀, SO₃, Cl₂O₇ - Al₂O₃ is amphoteric

Why does not SiO₂ really react in water?

It is a network covalent compound

How do you determine if the formation of an ion is an endothermic or exothermic reaction?

Generally, removing electrons from an atom will be an endothermic while adding electrons to an atom will be an exothermic reaction. (most atoms want more electrons to obtain noble gas configuration so its easier to add e-)

If you are trying to bond two anions or two cations to each other, however, it will be an endothermic reaction because they will require more energy to bond as they are opposite charges.

How do you determine which pair of elements in a set reacts most readily?

The most reactive element of one group will always be most reactive with the most reactive element of another group, look for high electronegativity differences