Introduction to Chemistry: Matter and

its InteractionsMr. Pierson

Fall 2013

Atoms

• Consist of protons, neutrons, and electrons• Protons – positively charged subatomic particle found in the nucleus

• Electrons – negatively charged subatomic particle outside of the nucleus

• Neutrons – neutrally charged (no charge) subatomic particle found in the nucleus

The Periodic Table

• Elements – simplest forms of matter that can exist under normal laboratory conditions.• Matter – anything that takes up space and has mass.

• Mass – the amount of matter that an object contains.

• The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns.• Chemical property – the ability of a substance to undergo chemical reactions

and to form new substances.

Important Things to Learn Right Away• Symbols of Common Elements• Symbols of Common Polyatomic Ions• The Periodic Table• Alkali metals• Alkaline earth metals• Nonmetals• Noble gases

The Alkali Metals

• Li• Na• K• Rb• Cs• Fr

Alkaline Earth Metals

• Be• Mg• Ca• Sr• Ba• Ra

Nonmetals

• B• C, Si• N, P, As• O, S, Se, Te• F, Cl, Br, I, At

Noble Gases

• He• Ne• Ar• Kr• Xe• Rn

Metals, Nonmetals, Metalloids

• Metals – elements that have a high electrical conductivity and a high luster when clean.• Nonmetals – elements that are nonlustrous and are generally poor

conductors of electricity.• Example: Argon, Chlorine (gases); Carbon, Sulfur (solids); Bromine (liquid at

room temp.)

• Metalloids – elements with the properties of both metals and nonmetals.• Example: Silicon and Germanium

Assignment

• Pg. 109, “Concept Practice” #1• Pg. 136, “Practice Questions and Problems” #32• Pg. 137, “Mastery Questions and Problems” #54• List the symbol and names of the Alkali Metals, Alkaline Earth Metals,

Nonmetals, and Noble Gases

Atoms and Ions

• Ions- atoms or groups of atoms that have a positive or negative charge.• Cations – any atom or group of atoms with a positive charge

• Has less electrons than protons• Example: Na+

• Has 11 protons and only 10 electrons when it loses an electron (with 1 more proton only the “+” is used, if 2 more protons than electrons we would write “2+” to represent that there are 2 more protons than electrons)

• Anions – atoms or groups of atoms with a negative charge• Has more electrons than protons

• Example: Cl- • Has 17 protons and 18 electrons when chlorine gains an electron. Remember, electrons

are negatively charged, so in this case we have 18 negatives and 17 positives for an overall -1 (17-18).

Compounds

• Molecule – an electrically neutral group of atoms that act as a unit.• Example: H2O

• Water is a molecular compound – compounds that are composed of molecules

• Ionic Compound – composed of positive cations and negative anions.• Example: NaCl

• Chemical formula – shows the number and kinds of atoms in the smallest representative unit of the substance.• Molecular formula – shows the number and kinds of atoms present in

a molecule of a compound.

Compounds, cont.

• Chemical compound (compound = 2 or more things combined)

• Molecular (2 or more molecules)• Ionic (2 or more ions)

• All different compounds have different properties

• Must use chemical formula (remember, a chemical symbol is the same thing as an element symbol, i.e. H, He, etc.)

• If the chemical is a molecular compound, then a molecular formula is used• Example: H2O

Formula Units

• = the lowest whole-number ratio of ions in an ionic compound.• Example: Sodium Chloride

• Na+ needs 1 electron and Cl- has 1 extra electron, the ratio is 1:1, thus the formula unit is NaCl.

• Mg2+ needs 2 electrons and Cl- has 1 extra electron, so it would take 2 Cl- anions to combine with the Mg2+ cation, thus the ratio is 1:2 and the formula unit = MgCl2

• What would the formula unit be for Li+ and S2- ions?

In-Class Assignment

• Read pg. 116 – 123• Copy Table 5.4 “Common Polyatomic Ions” into your notes.