Atoms & The Periodic Table

ATOMIC STRUCTURE Atoms are made up of 3 subatomic particles: positive neutral negative In nucleus Outside nucleus

Atoms and the periodic table O oxygen The atomic number is the number of proton in an element. The atomic mass is equal to the number of protons plus the number of neutrons in an atom.

Information from the periodic table The atomic number = number of protons. The number of electrons = the number of protons. The atomic mass when rounded to the nearest whole number is called the mass number. If you subtract the number of protons from this number, you will determine the number of neutrons in the nucleus. # neutrons = mass number - # of protons The electron configuration shows how many electrons there are in each energy level. 2 electrons go in the first shell, 8 in the second, 8 in the third. Valence electrons are the electrons in the outer energy level of the atom.

Practice Questions 1.Determine the # of Protons, Neutrons and Electrons. 2.Draw the electron configuration. 3.Determine the number of valence electrons.

Answers 1.p= 11, n= 12, e- = valence electron 11p 12n 8 2 1

Periods are rows on the Periodic Table. Elements in a periods all have the same number of energy levels. If the element is in period 3, it has 3 energy levels.

Groups or families are the columns on the periodic table. Elements in a column or family or group have similar chemical properties because they have the same number of valence electrons.

Metals and Nonmetals Metals are found on the left of the zig-zag on the periodic table. Metals have 3 or less valence electrons. Metals give electrons. Metals are good conductors of heat and electricity. Nonmetals are found on the right of the zig-zag on the periodic table. Nonmetals have 5 or more valence electrons. Nonmetals take electrons. Nonmetals are poor conductors of heat and electricity and are brittle. Metalloids are along the zig-zig line and have properties of both metals and nonmetals.

Bonding Elements bond by exchanging electrons. This is called an ionic bond. Elements that have less than 4 valence electrons, give electrons. This tends to be elements in families 1-3 (metals). Elements that have more than 4 valence electrons, take electrons. This tends to be elements in families 5-7 (nonmetals).

Practice Questions 1.Is this element a metal or nonmetal? 2.Would this element give or take electrons? 3.Name an element that is chemically similar to this element. 4.Name an element this element would most likely bond with.

Answers 1.Metal 2.Give 3.Any element in the same family. For example, Sodium. 4.Any element that would take 1 electron (family 7). For example, Fluorine.

TYPES OF CHEMICAL REACTIONS Synthesis reaction: 2 simple substance combine to form a more complex substance A + B  AB Decomposition reaction: a complex substance breaks down into 2 or more simple substances AB  A + B Single replacement reaction: an element replaces an element in a compound A + BC  AC + B Double replacement reaction: 2 elements replace each other in 2 compounds AB + CD  CB + AD

Types of Reaction Practice 1.Cs + N 2 → Cs 3 N 2. NaBr + Cl 2 → NaCl + Br 2 3. Cs 3 N → Cs + N 2 4. C 10 H 16 + Cl 2 → C + HCl 5. HCl + NaBr → NaCl + HBr Synthesis Single Replacement Decomposition Single Replacement Double Replacement

Chemical reactions continued Each chemical equation must be balanced so that all the atoms of each element are the same on both sides of the arrow. The Law of Conservation of Mass: matter cannot be created or destroyed during a chemical reaction A chemical reaction that absorbs energy and feels cold is ENDOthermic. A chemical reaction that releases energy and feels warm is called EXOthermic. To increase the rate of a chemical reaction you can: – Heat it up – Increase the surface area of the substance – Increase the concentration of the reactants

ACIDS AND BASES pH is measured by using a scale that goes from 0 to 14. Lower than 7 is an acid. Greater than 7 is a base. 7 represents a neutral pH. The further away from neutral, the stronger the acid or the base. Example: A pH of 12 would indicate a very strong base and a pH of 2 would indicate a very strong acid.

Neutralization If you add an acid and a base together a special type of reaction happens. Neutralization- a reaction between an acid and a base. When an acid is added to a base, a salt and water is produced and the pH= 7. ACID + BASE  SALT + WATER