Atoms and the Periodic Table

Basic Definitions Chemistry is the study of the composition, structure, and properties of matter and the changes it undergoes.

More Intro Stuff Chemistry can deal with questions like: What is this material made of? What type of things will this substance react with? Why is carbon dioxide transformed by plants into oxygen?

17.1 Atom: is the smallest unit of an element that has the same properties of that element. Element: is a pure substance composed of only one kind of atom. Compound: is a substance that is made of two or more elements that are chemically bonded together.

Atoms are old! Hydrogen is the oldest and most abundant element The atoms in your body existed since the beginning of time We recycle atoms!

Atoms Composition Protons – positive parts in the nucleus Neutrons- neutral parts in the nucleus Electrons- small negative parts around the nucleus The movement of electrons is electricity!

Periodic Table Periodic table: is a grouping of elements in order of increasing atomic number. Atomic symbol: the letters by which the element is designated Frequently from the Latin name First letter capital, second lowercase (Si)

17.2 Atoms are mostly empty space Everything around us is mostly empty space…huh? We don’t fall into each other because your electrons repel my electrons… like a magnet…we push off before we fall in like a ghost! You know you never actually touch someone…WHAT??!

Craziness Cont The repelling electrical fields create the feeling of touch, but there is always a layer of electrons between you and the other person.

17.3 Protons are 2000 times larger than electrons, but have the same charge The number of protons in an atom equals the atomic number All elements have a different atomic number. (elements fingerprint) Note: In an atom, the number of protons is equal to the number of electrons.

Isotopes atoms of the same element with a different mass because of a different number of neutrons. The number of neutrons in an atom can change, but the proton number will always remain the same.

Designating Isotopes There are two ways to designate isotopes: Hyphen notation is when you write out the element name followed by a hyphen and the mass #.Calcium – 40 Nuclear notation is when the element symbol is written, then in the upper left is the mass number. 40 Ca

17.4 (Write this down, practice tomorrow!) # neutrons + # protons = mass number # neutrons = mass number – atomic number

17.5/ Periodic Table Vertical columns on a periodic table are called groups or families. (label your table!) Horizontal rows on a periodic table are called periods. The periods are numbered Period 1 to 7.

Metals vs. Nonmetals vs. Metalloids Metals left side of the periodic table good conductors of heat and electricity malleable (can be hammered into sheets) ductile (rolled into wire)

Metals vs. Nonmetals vs. Metalloids Nonmetals right side of the periodic table poor conductors of heat and electricity gases or brittle solids. Metalloids have properties of metals and nonmetals.

Periodic Table Across the periodic table the properties of elements gradually change – periodic trend Example: atoms get smaller as your move from the left to the right Down the periodic table the elements properties are very similar…hence the names “group or family”

Periodic Table Families Group 1 – Alkali Metals Group 2 – Alkaline Earth Metals Group 3-12 Transition Metals Group 16 – Chalcogens Group 17 – Halogens Group 18 – Noble Gases

Alkaline Metals Middle ages, ash mixed with water….alkaline metals Alkaline Earth Metals Alkaline solutions in water, didn’t melt in fire “earth” Chalcogens “ore-forming” oxygen and sulfur common in ores Halogens “salt-forming” NaCl (table salt) Transition Metals Lanthanides (inner transition metals)..some used in LED’s Actinides (inner transition metals)…nuclear power industry, uranium and plutonium

Noble Gases The Noble Gases are group 18 very stable do not like to react with anything Most of the Noble Gases are used in lighting, and helium is used to inflate balloons so that they float.