Organization, Names, Trends, and Properties The Periodic Table Organization, Names, Trends, and Properties

Review What is an isotope? What value determines the number of protons? Electrons? What is the mass number and how can we use this to determine the number of neutrons? Review

The three isotopes of chromium are chromium-50, chromium-52, and chromium-53. How many neutrons are in each isotope, given that chromium always has an atomic number of 24? Isotopes

The Periodic Table!!

Elements vary widely in their patterns, but in a very orderly way. Elements in a similar row have similar chemical and physical properties. Dmitri Mendeleev organized the elements based on their sets of properties. Periodic Pattern

The Periodic Law states that when the elements are arranged according to their atomic numbers, elements with similar properties appear at regular intervals The Periodic Law

Elements in each column have the same number of electrons in their outer most level. These outer most electrons are known as the valence shell electrons These valence electrons are the ones that do all the reacting and interacting. Valence Electrons

Valence Electrons

A vertical column on the periodic table is known as a group A horizontal row on the periodic table is known as a period Elements in the same period have the same number of occupied energy levels. Elements in the same group tend to react the same (same number of valence electrons) Arrangement

Elements in groups 1, 2 and 13-18 are known as the main-group elements The electron configurations of the elements in each main group are regular and consistent. The elements in each group have the same number of valence electrons Ex: elements in group 2 all have two valence e-’s ns2, where n is the period number The main-group elements are sometime referred to as representative elements Main Group Elements

Noble Gases Group 18 elements are known as the noble gases Octet Rule = 8 outermost electrons (STABLE) They HAVE their octet achieved already (8 valence electrons) Soooooo, are they reactive???? It is the full outer shell than lead scientists to believe 8 was nonreactive, not the other way around Noble Gases

Halogens Elements in Group 17 are known as the halogens The halogens are the MOST reactive group of nonmetal elements because they are soooo close to achieving their octet (they have to STEAL one electron) React with most metals to form salts In fact, the name halogen is Greek for “salt maker.” Halogens

Alkaline-Earth Metals Group 2 elements are called the alkaline-earth metals Also, HIGHLY reactive Because they are highly reactive they are usually found as compounds rather than as pure elements. Slightly less reactive than the alkali metals because they have two electrons to get rid of instead of just one to achieve the octet rule Alkaline-Earth Metals

Alkali Metals Elements in Group 1 are called alkali metals Name this because they all react with water to make alkaline (basic) solutions Ex: K reacts vigorously with H2O to yield KOH Because alkali metals have ________ valence electron(s) they are __________ reactive. They need to ________________ to obtain their octet. Alkali Metals

Hydrogen is Special Hydrogen is in a class all by itself It is the MOST COMMON element in the universe Roughly 3 out of every 4 atoms in the universe is H Hydrogen has _________ electron(s) but wants _______. Does not follow the ______________ rule Hydrogen is Special

Metals Most elements are metals All metals are excellent conductors of electricity Great conductors of heat Ductile (can be squeezed into a wire) and malleable (can be pounded into shape) Alloys are mixtures of elements, giving them a mixture of properties  eliminate bad properties and give the good ones. Metals

Transition Metals are groups 3–12 (we know them as??) Sometimes called the d-block b/c of their position DO NOT have the same number of valence electrons This causes the varying charges May lose or gain DIFFERENT numbers of electrons depending on who its bonding with (again, explaining the varying charges) Also good conductors or heat / electricity Transition Metals

f - Block Lanthanides and Actinides Lanthanides - Shiny metals similar in reactivity to the alkaline-earth metals Actinides – Nuclei are unstable, making all of them radioactive. The best known actinide is U, or _______________. f - Block

Electron Shielding blocks the outer electrons from the inner nucleus attraction, making them less tightly held. Electronegativity decreases from right to left and top to bottom. Atomic radius increase from right to left and top to bottom. (The “F” rule) Ionization Energy decreases right to left and top to bottom. Periodic Trends

Electronegativity – a measure of the ability of an atom in a chemical compound to attract electrons Decreases as you move down a group Decreases Decreases Electronegativity

Atomic Radius – the overall size of the energy levels surrounding the atom “F-rule” = Francium is HUGE and Fluorine is TINY Increases Increases Atomic Radii

Ionization Energy – the energy required to remove an electron from an atom or ion. (Decreases down and to the left) Decreases Decreases Periodic Trends

Average Atomic Mass These are relative atomic masses Why are the atomic masses of most elements on the periodic table not exact whole numbers? These are relative atomic masses Most have isotopes and are a mixture of these differently massed species. Average Atomic Mass

Most Elements are Mixtures of Isotopes The periodic table reports Average Atomic Mass, a weighted average of the atomic mass of an element’s isotopes. Example: If I said there was a larger abundance of C-12 than C-13, which value would the average atomic mass be closer to? Most Elements are Mixtures of Isotopes

Calculating Average Atomic Mass If you know the abundance of each isotope, you can calculate the average atomic mass of an element. The mass of a Cu-63 atom is 62.94 amu, and that of a Cu-65 atom is 64.93 amu. Abundance of Cu-63 is 69.17% and Cu-65 is 30.83%. Find the average atomic mass of Cu. Calculating Average Atomic Mass

Calculate the average atomic mass for gallium if 60 Calculate the average atomic mass for gallium if 60.00% of its atoms have a mass of 68.926 amu and 40.00% have a mass of 70.925 amu. Calculate the average atomic mass of oxygen. Its composition is 99.76% of atoms with a mass of 15.99 amu, 0.038% with a mass of 17.00 amu, and 0.20% with a mass of 18.00 amu. More Practice

Calculate the molar mass for each of the following compounds: CsI C12H22O11 HC2H3O2 CaHPO4 I2 Mg3(PO4)2 Molar Masses