1) Atoms are made up of protons, neutrons, and electrons. Protons and neutrons are located in the nucleus, while electrons orbit around the nucleus. 2) The atomic number of an element is the number of protons it contains. Isotopes are elements with the same atomic number but different numbers of neutrons. 3) Elements are arranged in the periodic table based on their atomic number. The periodic table is organized into rows and columns, with elements in the same column having similar chemical properties.

1. Atoms, Elements, and the Periodic Table

2. Atoms Atoms are the building blocks of matter The modern atomic model describes an atom as consisting of: Nucleus that contains: Protons, neutrons , and electrons outside of the nucleus

3. Sub atomic Particles Protons Found in the nucleus Have a positive charge (+) Each element in the periodic table has its own specific number of protons

4. Subatomic Particles (cont.) Neutrons Found in the nucleus Have no charge (neutral)

5. Subatomic Particles (cont.) Electrons Found orbiting around the nucleus in electron clouds The exact location of electrons cannot be determined Electrons have a negative charge (-) In a neutral atom, the number of electrons= the number of protons

6. Atomic Number Atomic number is: The number of protons in an element Every atom of a specific element has the same number of protons Example: Hydrogen has 1 proton Carbon has 6 protons

7. Isotopes Isotopes of an element are: Elements having the same number of protons , but different numbers neutrons Examples: Carbon 12 , 6 protons+ 6 neutrons Carbon 13 , 6 protons+ 7 neutrons Carbon 14 , 6 protons + 8 neutrons

8. Mass Number Mass number is: The number of protons + neutrons in the nucleus of an atom

9. The Periodic Table In 1869, Dmitri Mendeleev developed the first periodic table based on atomic mass : (atomic mass= #protons+#neutrons in the nucleus of the atom) In 1913, Thomas Moseley developed the modern periodic table based on atomic number (atomic number= #protons in the nucleus of the atom)

10. The Periodic Table (cont.) Periodic means: Repeating according to a pattern The modern periodic table is arranged in columns and rows Columns go up and down (think of columns on a building) Rows go from left to right

11. The Periodic Table (cont.) Groups or Families Columns are called: Groups or Families There are 18 groups or families in the periodic table Elements in the same group or family have the same number of valence electrons Valence electrons are the number of electrons in the outer most energy level Group 1 has 1 valence electron

12. The Periodic Table (cont.) Groups or Families Group 1 has 1 valence electron 2 2 13 3 14 4 15 5 16 6 17 7 18 8 *Groups 3-12 do not follow this pattern

13. The Periodic Table (cont.) Periods Periods are the portion of the periodic table that go from left to right (think of when you write a sentence, you put a period at the end of the sentence. There are 7 periods in the periodic table. All elements in the same period , have the same number of energy levels . Energy levels are where the electrons are located

14. The Periodic Table (cont.)