chapter 5 – atomic structure atoms structure of an atom distinguish between atoms the periodic...
TRANSCRIPT
Chapter 5 – Atomic Structure
Atoms Structure of An
Atom Distinguish Between
Atoms The Periodic Table
Ch 5.1 Atoms
Democritus of Abdera (Greece)
4th Century BC Coined the term
“atom” Could not prove
because no scientific research was being done
John Dalton (1766-1844)
Conducted research as to the ratios of elements in compounds
From the research he came up with Daltons Atomic Theory
Dalton’s Atomic Theory
1. All elements are composed of tiny indivisible particles called atoms.
Dalton’s Atomic Theory
2. Atoms of the same element are identical. The atoms of one element are different from those of any other element.
Dalton’s Atomic Theory
3. Atoms of different elements can physically mix together or can chemically combine with one another in simple whole number ratios to form compounds.
Dalton’s Atomic Theory
4. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
Atom
The smallest particle of an element that retains the properties of that element.
Just How Small is an Atom
A pure copper coin about the size of a penny has 2.4 x 1022 atoms
2,400,000,000,000,000,000,000,000 atoms Earths population is only 6 x 109 people
Just How Small is an Atom
A 1cm long line of copper atoms has 100,000,000 atoms
Ch 5.2 Structure of the Nuclear Atom Particle Accelerators
are used to smash particles at speeds near the speed of light into each other in order to break them apart
A bubble chamber is used to track the paths of the broken particles
Cant ever see the actual particles
Electrons
Negatively charged subatomic particle
e-
Electrons
J.J. Thomson (1856-1940) discovered electrons in 1897
Invented cathode ray tubes (used in TVs)
Electrons
Robert Millikan (1868 – 1953)
Determined an accurate mass of an electron
Mass 1/1840 of a hydrogen atom
Protons
E. Goldstein (1886) discovered protons in a cathode ray tube
Protons are positively charged
Mass is 1840 times an electron
Neutrons
James Chadwick (1932) discovered neutrons
No Charge Mass the same as a
proton
Particle Symbol Charge Relative Mass
Actual Mass (g)
Electron e- 1- 1/1840 9.11x10-28
Proton p+ 1+ 1 1.67x10-24
Neutron n0 0 1 1.67x10-24
Atomic Nucleus
Rutherfords Gold Foil Experiment Shot rays of alpha particles at thin gold foil Most passed straight through Some bounced off at large angles Some bounced straight back Suggested that an atom is mostly empty
space with most of the mass and the positive charge in the center (nucleus)
Ch 5.3 Distinguish Between Atoms Atoms are made up
of Electrons Protons Neutrons
Nucleus contains protons and neutrons
Atomic Number
The number of protons in the nucleus of an element
Every element has a different atomic number
Atomic Number
The number of protons equals the number of electrons
Protons are positive, electrons are negative, therefore the total net charge of an atom is 0
Mass Number
The number of protons and neutrons.
Number of neutrons equals mass number minus atomic number
Mass Number
The number of protons does not always equal the number of neutrons
Oxygen Beryllium
Isotopes
There are different types of neon
What is different?
Isotopes
All of the neon's have the same number of protons and electrons, but different number of neutrons
Ne-20 has 10 Ne-21 has 11 Ne-22 has 12
Isotopes
Atoms that have the same number of protons and electrons but different numbers of NEUTRONS.
This also creates a different mass number for each.
Hydrogen
Atomic Mass
AMU (Atomic Mass Units) defined as 1/12 the mass of carbon-12 or 1 amu.
Atomic Mass
The weighted average mass of the atoms in a naturally occurring sample of the element.
Based on the percent of each isotope present on earth.
Atomic Mass
Chlorine 35 – 75.77% Chlorine 37 – 24.23 %
Average Mass based on Percents = 35.453