Periodic Table A periodic table is used to organize elements based on their physical and chemical properties including mass, conductivity and reactivity.

Periodic Table Mass (sometimes weight is used)- heaviness Conductivity- how well they carry an electric current Reactivity- the rate at which they react chemically

What are Elements? An element is a are pure substance (matter) that is made of only one type of atom. Helium- the gas used to inflate balloons (minus the balloons) Gold

What Is An Atom? An atom is the smallest unit of all matter.

Atom and Cell Analogy An atom is like a cell. It is the smallest unit (building block) of matter in the same way that a cell is the smallest unit (building block) of all living things.

Atoms make up: Cells make up:

Group #/column 18 Periods (rows) 1 2 13 14 3 4 5 6 9 10 11 12 13 14 Periods (rows) (Or atomic mass) 3 4 5 6 9 10 11 12

Periods and Groups Groups- these are the vertical columns Periods- these are the horizontal rows

Periods and Groups Most metallic

Periods and Groups Although they are getting heavier (atomic # increases) , protons pull electrons in tighter.

Periods and Groups

Element: Carbon Find Carbon on your periodic table. The atomic number can appear at the bottom or top of the element square.

What can the periodic table tell us about matter? Phase: Solid, Liquid, Gas 2. Material: Metal, non-metal, gas, radioactivity, whether it is natural or man-made. 3. How materials will behave: ability to conduct electricity and heat (copper), will rust (iron) and more….

It can also tell us about the elements’ structures Energy levels/orbits Bohr Models of aluminum, lithium and oxygen.

Bohr Models to illustrate the atomic structures of elements Atomic Modeling: using Bohr Models to illustrate the atomic structures of elements

Element: Carbon Let’s look at the element Carbon.

3. This is how many electrons you will draw. How to draw a Bohr Model 1. Find your element on the periodic table. (Carbon’s atomic # is 6) 2. Determine the number of electrons – it is the same as atomic number. 3. This is how many electrons you will draw.

Energy Levels Find out which Period (horizontal row) your element is in. Elements in the first period have 1 energy level. Elements in the second period have 2 energy levels, and so on…

Element: Carbon The atomic number for carbon is 6, therefore it has 6 electrons.

Drawing a Bohr Diagram Draw a nucleus with the element symbol inside. Carbon is in the second period so it has two energy levels or “shells”. Draw the shells around the nucleus. nucleus Energy levels (2)

Add the electrons- carbon has 6. 5. Start with the first energy level, the one nearest the nucleus and add 2. (The first energy level can only hold 2)

5. After you have added the first 2, you still have 4 more electrons left. These go on the 2nd level (shell). Start on the right side & work counter-clockwise.

Completed Bohr Model

Bohr Modeling Practice: Now try the following elements on your own. Start by using the symbol to find the element on the periodic table and writing its name next to your Bohr model. Then, find the number of electrons it has. H d) Al He e) Ne O f) K

Bohr Model You should now be able to draw a Bohr Model for the first 20 elements in the periodic table. Any Questions?

Atoms are made of 3 kinds of particles: Protons Neutrons Electrons Part 2- What’s in an atom? Atoms are made of 3 kinds of particles: Protons Neutrons Electrons

Electrons We already learned that electrons are particles that move in an atom’s energy levels or shells. They carry a negative charge and are shown like this: e-

Protons & Neutrons Protrons and neutrons are found in the nucleus of atoms.

Protons, Neutrons & Electrons Now that we know how to find the number of electrons in an element (its atomic number), how would you find the number of protons and neutrons it has?

Protons & Neutrons In general, the number of protrons in an atom is equal to the number of its electrons. The atomic mass is equal to the sum of the protrons and neutrons. Take the atomic mass and round it to the nearest whole number (if it is shown as a decimal), then subtract the atomic number to find the number of neutrons in the atom.

Example Copper has an atomic number of 29 and an atomic mass of 64. 35 So, copper has 35 neutrons, 29 protrons and 29 electrons.

Protons & Neutrons Protons and neutrons are found in the nucleus (or center) of an atom. Protons have positive (electrical) charges while neutrons have no charge. They are “neutral”.

What do the charges do? A normal atom has a neutral charge with equal numbers of positive and negative particles. That means an atom with a neutral charge is one where the number of electrons is equal to the atomic number. Ions are atoms with extra electrons or missing electrons. When you are missing an electron or two, you have a positive charge. When you have an extra electron or two, you have a negative charge. 

Compounds will be discussed in part 3. What do the charges do? When an atom has an unbalanced charge, it tries to share with other atoms in order to become neutral or “stable”. This is how compounds are formed. Compounds will be discussed in part 3.