Presentation on theme: "Atoms & Elements. What is an atom? An atom is the smallest particle of an element that retains its identity in a chemical reaction. Word origin: atom."— Presentation transcript:
What is an atom? An atom is the smallest particle of an element that retains its identity in a chemical reaction. Word origin: atom comes from the Greek word atomos meaning “ indivisible”
Elements & Compounds What would atoms of an element, mixture and compound look like at a microscopic level?
The parts that make up an atom! protons neutrons electrons Subatomic Particles nucleus proton neutron electron
Found in the nucleus Identifies the element #of protons = specific element Responsible for chemical and physical properties Found in the nucleus Plays no role in chemical behavior Purpose: to put space between protons Spin around in set regions outside of nucleus Most important in chemical reactions Farthest electron away from nucleus determines how atoms chemical to combine to one another. Subatomic Particles Electrons Neutrons Protons
NameSymbolChargeRelative Mass Protonp+p+ +11 Neutronnono 01 Electrone-e- 0 (1/1840) Subatomic Particles How big is an atom? Imagine the nucleus is the size of a marble located in the middle of the football field, the electron would be in the classroom the size of a period!
Counts the number of protons and neutrons in an atom OR Determined by: the whole number closest to the Atomic Mass Mass Number Important Numbers 14 Si Silicon 28.086 Atomic Mass
Show the mass number and atomic number Give the symbol of the element Atomic Symbols Mass Number 28 14 Si Mass Number Atomic Number silicon-28
Determine the Mass Numbers 4 Be 9.0122 27 Co 58.933 10 Ne 20.179 959 20
Write the Symbol and Name for each 4 Be 9.0122 27 Co 58.933 10 Ne 20.179 Be 9494 beryllium-9 59 27 Co cobalt-59 20 10 Ne neon-20
The total number of particles in the nucleus # of protons + # of neutrons To determine the number of neutrons Mass number – Atomic number = # of neutrons Mass Number 16 8 31 15 65 30 #p #n #e O PZn 8p + 8n o 8e - 15p + 16n o 15e - 30p + 35n o 30e -
Naturally occurring hydrogen consists of 3 isotopes, protium (H-1), deuterium (H-2), and tritium (H-3). State the number of protons, neutrons, and electrons. Isotopes of Hydrogen 1111 2121 3131 #p #n #e H H H 1 0 1 1 1 1 1 2 1
A. Number of protons B.number of neutrons C.What is the mass number of a calcium isotope with 19 neutrons? An atom of Calcium (Ca-40)
This is NOT a whole number A given element can have atoms with several different mass numbers. Average mass of the atoms with all possible mass numbers We will calculate later Atomic Mass
A.11p +, 12n o, 11e - B.17p +, 20n o, 17e - C.47p +, 60n o, 47e - Write the atomic symbol
A.11p +, 12n o, 11e - B.17p +, 20n o, 17e - C.47p +, 60n o, 47e - Write the atomic symbol 23 11 Na 37 17 Cl 107 47 Ag
Remember atoms are neutral, therefore if an atom has a charge we call it an ion. Ions - Atoms which gain or lose an electron Atoms with a charge (positive or negative) Ions atomion #p1111 #e1110 atomion #p1717 #e1718 Na 1+ Cl 1- Why do the electrons change?
If protons change…new______?________ If neutrons change…new______?______ If electrons change….new _____?______ Why?
If protons change…new element If neutrons change…new isotope If electrons change….new ion Why?
To find the Average Atomic Mass (generally referred to as the atomic mass of an element) we need to use two things The mass of the isotope Multiplied by its frequency Then we add all the forms up. Average Atomic Mass cont.
Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 75.526.4 35 x 75.5 = 26.4 100 35.5 24.5= 9.07 37 x 24.5 = 9.07 100 Example of Average Atomic Mass
Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass or rubidium?