This document provides a summary of atoms and molecules: - Atoms are the smallest particles that make up all matter and can be represented by models and symbols on the periodic table. - Atoms are made up of three subatomic particles - protons, neutrons, and electrons. Protons and neutrons are located in the nucleus, while electrons surround the nucleus. - For an atom to be neutral, the number of protons must equal the number of electrons. The number of neutrons can vary. The number of protons determines the element.

1. Chapter 23: Atoms and Molecules Hope this helps (:

2. Atoms Matter is anything that has mass and occupies space Matter is made up of atoms- particles that are too small to be seen with the eyes. An atom is the smallest particle of any element found in the periodic table. The sizes of atoms from the SAME ELEMENT are the SAME while those from different elements are different. Just remember, same same, different different. Atoms are represented by models, circles and symbols. H O Na Fe Hydrogen Oxygen Sodium Iron

3. Structure of Atoms An atoms is made up of 3 smaller kinds of particles called subatomic particles. Ther are NEUTRON, PROTON, ELECTRON. Atom is mainly made out of empty space, the necleus house the neutron and proton while the electron is housed by the membrane. O2-> 2 oxygen atoms in one molecule. Electron Proton Neutron

4. Table that summarizes the characteristics of each subatomic particle Outside the nucleus -1 Almost 0 Electron In the nucleus 0 1 Neutron In the nucleus +1 1 Proton Location Relative Electric Charge Relative Mass Particle

5. The nucleus is positively charged as it is made up of protons and neutrons. It is surrounded by negatively charged electrons, moving around in shells. The nucleus is the heaviest part of the atom as the electrons around it have negligible mass. An atom is ALWAYS NEUTRAL. HENCE in an atom, *** The number of protons (+) = the number of electrons (-)

6. If an atom has 3 positively charged protons, it will have 3 negatively charged electrons. Protons and Electrons have the same number. The number of neutrons may vary, it may be 3 or 4 neutrons. If an atom has 10 positively charged protons, it will have 10 negatively charged electrons as well. Then, the atom is neutral, it will have 10 neutrons and there may be more or less neutral neutrons.

7. THE NUMBER OF PROTONS IN AN ATOM is called the PROTON number or ATOMIC number. Each element in the periodic table has its own proton number. The NUMBER OF PROTONS AND NEUTRONS IN THE NUCLEUS IS CALLED THE NUCLEAN NUMBER OR MASS NUMBER They can be represented by symbols such as 12 C 6

8. That symbol shows a carbon atom with a proton number of 6 and a nucleon number of 12. It means that carbon has 6 positively charged protons and it has 6 negatively charged electrons, it is a neutral atom. Try it Element: Sodium Total Number of: Protons: Electrons: Neutrons: (Refer to periodic table for question above and below, fill in the blanks)

9. 8 8 Oxygen 40 Ca 20 12 24 Magnesium 18 17 17 17 35 35 Cl 17 Chlorine 0 1 1 1 1 1 H 1 Hydrogen No of neutrons No of electrons No of protons Proton No Nucleon No Symbol Atom

10. Sorry, I stopped here first, cause I am a bit tired too. However I hope this helped (: I will continue the rest like tomorrow (: