Structure of an Atom

Atoms Smallest particle of matter All atoms of the same element are basically the same atoms of different elements are always different

Parts of Atom Nucleus Center of an atom 2 parts: Protons Neutrons Positive charge Mass= 1 amu Neutrons Neutral- no charge

Electron Negative charge Located outside nucleus Always in motion some distance from nucleus in the electron cloud Mass is very small in relation to the mass of the proton or neutron (so it is negligible in calculating the mass of an atom)

Practice Problem 1 What is the net charge on a particle that consists of 15 protons, 16 neutrons and 18 electrons? -3

Practice Problem 2 What is the net charge of a particle that contains 10 protons, 9 neutrons and 8 electrons? +2

Practice Problem 3 What is the net charge of a particle that contains 1 proton, 0 neutrons and 1 electron? 0

Practice Problem 4 Where is most of the mass located in the atom? In nucleus

Practice Problem 5 If an atom has 9 protons and 10 neutrons, how many electrons must it have? 9 electrons

Complete Structure of Atom Review Worksheet

Atomic number = Number of protons Each atomic number is specific to a certain element No two different elements have the same atomic number or number of protons Periodic table is set up in order of increasing atomic number

Practice Questions How many protons are in oxygen? 8 Potassium (K) has how many protons? 19 Which has more protons, Lithium (Li) or Sodium (Na)? Na

If you are talking about a particular element, the number of protons will never change even if the charge changes. If this is the case, what must change in order for the charge to change? Number of electrons

If atom is neutral, # protons = # electrons How many electrons are in a neutral atom of Carbon? 6 If an atom is neutral and contains 1 proton, what element is it? Hydrogen (H) How many electrons are in a neutral atom of Zinc? 30

All atoms of an element are not necessarily identical They have same physical and chemical properties can have different numbers of neutrons This causes atoms to have different masses Atoms of the same element with different masses are called isotopes.

Isotopes Always have the same number of protons Have same atomic number Different numbers of neutrons Different masses (mass numbers) mass of atom = number protons + number of neutrons Isotope symbol

What do you know about this isotope?

Ions Charged element Positive ions: # protons > # electrons Negative ions: # protons < # electrons

Another Isotope symbol C - 13 Symbol – mass number