The Nucleus Chapter 14 Section 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

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

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

Parts of the Atom Particle Charge Location Weight Proton Positive (+) Nucleus 1 amu Neutron Neutral (no charge) Electron Negative (-) Electron cloud 0.018 amu amu = atomic mass unit

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-

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

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

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

Isotopes of Carbon Carbon-12 Carbon-13 Carbon-14 Mass Number 12 13 14 # protons 6 # neutrons 7 8 # electrons Atomic Number Average atomic mass—average mass of the mixture of an element’s isotopes

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