Name the steps of the scientific method in order February 15 Bellwork Name the steps of the scientific method in order

What is an Atom? The smallest particle of matter that still has all of the properties and characteristics of that type of matter. A copper atom is the smallest particle of copper that still has all properties of copper.

Brownian motion – the perpetual movement of particles (jiggling atoms) named after Robert Brown (Scottish Botanist) https://www.youtube.com/watch?v=8IlxsEzTbxw&feat ure=player_embedded

What Do Atoms Look Like? An atom is mostly empty space and contains what we call subatomic particles. They are electrons, protons and neutrons.

Subatomic Particles Protons with a positive charge found in the nucleus of an atom Neutrons with a neutral charge also found in the nucleus of an atom Electrons with a negative charge found outside of the nucleus in the electron cloud

The Periodic Table The elements are arranged according to characteristics in a grid-like structure, both how they look as well as the way they act Each box represents an element and each box contains the Atomic number (number of protons/electrons) Atomic mass number Chemical symbol

Atomic Number The smaller number with no decimals Represents the number of protons and electrons in a neutral atom Periodic trend: increases from top to bottom and from left to right Example: If the atomic number is 2, then the atom has 2 electrons and 2 protons. Example 2: K has _19_ protons and _19_ electrons when neutral

Atomic Mass Number The larger number with a decimal Measured in amu (atomic mass units) Represents the number of protons and neutrons in an atom Atomic Mass # = protons + neutrons

Therefore… To find the number of neutrons: Neutrons = mass number – atomic number

Example Carbon has a mass number of 12.011 and an atomic number of 6. How many protons does it have?

Chemical Symbol Single letters or first letter capitalized If there are 3 letters, it is a man-made element that may get renamed Gold – Au (aurum) Iron – Fe (ferrum)

Any element with an atomic number greater than 92 is man- made

Isotopes Atoms of the same element with the same number of protons but different number of neutrons The mass number is an estimate of all of the possible isotopes of each element Isotopes are the reason that there is usually a decimal point in the atomic mass number

Example of an Isotope C-12 has 6 neutrons, C-14 has 8 neutrons C-12 is more often found in nature, so the atomic mass of C is 12.011 which is closer to 12 than 14

How the Periodic Table is Set up Metals, Nonmetals, Metalloids Families (rows) and Periods (columns)

Metals Located to the left of the zigzag (except hydrogen and metalloids) Properties: Luster (shine) Can be stretched and shaped Good conductors of heat/electricity

Nonmetals Located to the right of the zigzag Properties: Dull Poor conductors of heat/electricity

Metalloids/Semi-metals/Semi-conductors Along the zigzag: B, Si, Ge, As, Te, Po Properties: Some are shiny but some are dull Not as good of conductors as metals but better than nonmetals

Periods (Rows) and Families (Columns) Rows/Periods Horizontal Elements in the same period don’t have the same properties 7 on the periodic table

Periods (Rows) and Families (Columns) Columns/Families Also called groups Vertical Elements in the same group/family have common properties 18 on the periodic table

Li, Na, K all have a similar chemical reaction with water (H2O) They all create an explosion that releases hydrogen gas (H2) Therefore, they are stored with oil, not water.

Valence Electrons The number of electrons in an atom’s outermost energy level Elements in the same group/family have the same number of valence electrons

Atoms want to achieve a filled outermost energy level we call this an “octet” if the energy level contains 8 valence electrons

Each Family of Elements Has its Own Name Alkali Metals Alkaline Earth Metals Transition Metals Halogens Noble Gases

Alkali Metals Group 1 elements (except H) Have 1 valence electron Are the most active metals Tend to react with group 7 elements (halogens)

Alkaline Earth Metals Group 2 elements Have 2 valence electrons Less reactive than alkali metals but still reactive Tend to react with group 6

Transition Metals Groups 3-12 on periodic table Metals, but different from alkali or alkaline earth metals Most have 1 or 2 valence e-s Include mercury (Hg) – the only liquid metal at room temperature

Halogens Group 7 elements Some are gas, Br is liquid, and some are solid Have 7 valence e-s Tend to react with group 1 elements (alkali metals)

Noble Gases Group 8 elements Helium has 2 valence e-s Ne, Ar, Kr, Xe, Rn, all have 8 valence e-s Are not reactive since they already achieved an octet Make up less than 1% of earth’s atmosphere Oxygen (21%), nitrogen (78%) contribute to most of the atmosphere

Rare-Earth Elements Includes elements at bottom of periodic table (periods 6&7) First row = lanthanoid series (tend to be metals) Second row = actinoid series (most are man- made and radioactive)

Names and Symbols of Commonly Used Elements Aluminum (Al) Boron (B) Calcium (Ca) Carbon ( C ) Chlorine (Cl) Copper (Cu) Helium (He) Hydrogen (H) Iron (Fe) Nitrogen (N) Oxygen (O) Sodium (Na) Gold (Au)

We Can Use the Periodic Table to Draw Bohr Models A.k.a “planetary models” Protons, neutrons and electrons are represented in the Bohr Model We know that protons and neutrons are located in the nucleus at the center The electrons are located in the electron cloud in energy levels

Energy Levels 1st level holds a max of 2 e- 2nd level holds a max of 8 e- 3rd level also holds 18 e-

Lewis (Dot) Diagrams Electron dot diagrams are structures that show the valence electrons as dots Valence electrons are the electrons in the outermost shell and can be determined by looking at the group number on the periodic table Groups 1A – 8A (SKIP TRANS. METALS)

If an element is in group 1A it has 1 V. E If an element is in group 1A it has 1 V.E. If an element is in group 5A is has 5 V.E.

Drawing Lewis Diagrams To draw the diagram: Write the symbol down Place dots around the symbol, one on each side and then begin to pair them