1. Structure of an Atom

2. What Is an Atom? An atom is often referred to as the building blocks of matter subatomic proton neutronelectron Atoms are composed of smaller subatomic particles such as the proton, neutron, and electron. They have a nucleus surrounded by an electron cloud element Each element is composed of one type of atom and can not be broken down into a simpler substance

3. Inner Structure of an Atom Nucleus - Small, dense, positively charged center of the atom which contains most of the atom’s mass The nucleus contains subatomic particles have certain characteristics:  Protons  Protons - positively charged particles in the nucleus of the atom  Neutrons  Neutrons - particles in the nucleus that have no charge but contribute to the atom’s mass

4. Outer Structure of an Atom ● Electron cloud ● Electron cloud - an area encircling the nucleus where electrons are likely to be found energy levels ● The cloud contains energy levels  electrons  electrons are negatively charged particles located in specific energy levels  energy levels completely surround the nucleus  there is a specific order for the electrons to fill the energy levels

5. Outer Structure of an Atom ● Energy levels ● Energy levels completely surround the nucleus Maximum of 2 electrons Nucleus Maximum of 8 electrons Maximum of 18 electrons Maximum of 32 electrons Maximum of 50 electrons

6. Outer Structure of an Atom ● valence electrons ● valence electrons are in the outermost energy level and are the electrons involved in bonding  valence is the number of bonds an atom can form  an atom is most stable when its outermost energy level is full

7. Atom Characteristics atomic number The number of protons in the nucleus is the atomic number of that atom. The number of protons (+) equals the number of electrons (-) atomic mass The atomic mass is the mass of the protons plus the mass of the neutrons  Atomic mass is reported in the SI units atomic mass units amu atomic mass units (amu)  Protons and neutrons each are given an amu of 1  Electrons have a mass of nearly zero

8. An atom recap An atom has three parts: Proton = positive Neutron = no charge Electron = negative Picture from http://education.jlab.org/qa/atom_model_03.gif The proton & neutron are found in the center of the atom, a place called the nucleus. The electrons orbit the nucleus.

9. What are elements? Elements are the alphabet to the language of molecules. To make molecules, you must have elements. Elements are made of atoms. While the atoms may have different weights and organization, they are all built in the same way.

10. Decoding Atom Information C carbon 6 12.0 Atom’s symbol Atom’s name # of protons Atomic mass

11. Decoding Atom Information cont: carbon 12.0 # of protons = # of electrons Atomic mass = # of protons plus the # of neutrons 6 C

12. Created by G.Baker www.thesciencequeen.net Atom Models There are two models of the atoms we will be using in class. Bohr Model Lewis Dot Structure

13. Bohr Model The Bohr Model shows all of the particles in the atom. In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N. In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. + + - -

14. Lewis Dot Structure The Lewis Dot Structure is a bit different from the Bohr model. It only shows the element symbol and it’s outer most electron shell. O ++ ++ + + + + - - - - -- - -

15. Electrons have special rules…. You can’t just shove all of the electrons into the first orbit of an electron. Electrons live in something called shells or energy levels. Only so many can be in any certain shell.

16. Nucleus 1 st shell 2 nd shell 3 rd shell Adapted from http://www.sciencespot.net/Media/atomsfam.pdf

17. What we need to know -number of protons -remember our energy levels Draw an atom of Sodium (Na) -look at Periodic Table So let’s try it….