The Nucleus

1. The Nucleus Chapter 14 Section 2

2. What is an Atom? • Most basic units of matter • Everything in world made up of atoms • Air you breathe • Desk you are sitting in • Your body • Smallest particle of an element with all the properties of the element that can combine with other atoms to form a molecule

3. How many different types of Atoms are there? • 92 naturally occurring atoms • 25 synthetic atoms (made by scientists in laboratory)

4. What is an Element? • Matter made of atoms of only one kind • Example: piece of aluminum foil • Element Aluminum—many of same kind of atom • Each atom has same properties: shiny, metal, flexible

5. Parts of the Atom amu = atomic mass unit

6. Two-Dimension Model • Protons & neutrons placed together in center—nucleus • Electrons orbit nucleus in space called electron cloud • Electron cloud organized into energy levels • 1st level—can hold 2 e- • 2nd level—can hold 8 e- • 3rd level—can hold 18 e-

7. Identifying Numbers • How does the nucleus in an atom of one element differ from the nucleus of an atom of another element? • Atoms of different elements contain different numbers of protons

8. Identifying Numbers • Atomic Number—number of protons in the nucleus of an atom • Hydrogen, smallest atom, has 1 proton • Uranium, heaviest natural atom, has 92 protons • atoms are identified by the number of protons • The number never changes without changing identity of element

9. Identifying Numbers • Isotopes –atoms of the same element that have different numbers of neutrons • element carbon has 6 protons (atomic number) • Isotopes of carbon can have 6, 7, or 8 neutrons • Mass number—number of neutrons plus the number of protons

10. Isotopes of Carbon Average atomic mass—average mass of the mixture of an element’s isotopes

11. Synthetic Elements • Elements that are made in labs by smashing atomic particles into a target element • Elements with atomic numbers 93 to 112, and 114 are synthetic elements