Atoms and the Periodic Table

By the end of this unit, you should be able to explain:

Why you share atoms with all the famous people of the world!

How people can see you if atoms are 99% empty space

Why this happens!

How the heck to read this!

Atoms & Stuff Atoms are recycled, recombined, broken apart, reconfigured, recycled, recombined, broken apart, reconfigured, recycled… The atoms in your body have been around since Time Zero They have been a part of many different things before you When you die (or exhale), they will be redistributed to other things Soil, plants animals and even other people (yuck!) You are made up of atoms that once belonged to dead people!

Atoms The smallest part of matter that retains the characteristics of that type of matter. Considered to be the building blocks of matter. Atoms consist of a positively charged center, or nucleus, surrounded by negatively charged particles. The nucleus consists of protons and neutrons. Negatively charged particles are called electrons, they exist outside the nucleus in mathematical ‘regions of probability.

Atoms Atoms are made of: Electrons Protons Neutrons The number of these particles in an atom determine what the atom is

Atoms PROTONS: Mass= 1.67 x 10 -24 g or 1 amu Are nucleons (located inside the nucleus) Have a positive charge

Atoms NEUTRONS: Mass= 1.67 x 10 -24 g or 1 amu Are nucleons (located inside the nucleus) Have a neutral charge

Atoms ELECTRONS Mass=9.11 x 10 -28 g or 1/2000 amu (negligible) Are not nucleons Outside the nucleus (electron cloud) Are negatively charged

Twig- Structure of atom http://www.twigcarolina.com/search/alt/?q=atom

Just how big is an atom? An atom is as many magnitudes smaller than a person as an average star is larger than a person. Put another way, an atom is to the size of an apple as an apple is to the size of the Earth. So if you want to imagine an apple full of atoms, think of the Earth packed full of apples!

Atoms to Elements to Atomic Symbols Each different type of atom is an element Elements are distinguished by the number of PROTONS. # of protons = atomic number Every atom of the same element has the same number of protons. Ex: Every atom of hydrogen has 1 proton Every atom of gold (Au) has 79 protons

Atoms to Elements The elements are identified by using their chemical symbol Always a capital letter for a single-letter atomic symbols Oxygen (O), Hydrogen (H) A capital letter is followed by a lower case letter for two-letter atomic symbols Helium (He), Iron (Fe), Titanium (Ti) Some symbols are derived from Latin names (ex: Argentum is Latin for silver; the symbol for silver is Ag)

IONS ARE ATOMS WITH OVERALL CHARGES In a neutral atom… # of protons = # of electrons (# of positives = # of negatives) When the number of protons and electrons are not the same, the atom has an overall charge (positive or negative). It is now an ION.

Types of IONS Cation = Positively charged atom (lost electron(s)) Anion = Negatively charged atom (gained electron(s))

The Charge of an Ion Charge of an ion = number of protons – number of electrons

ISOTOPES Different numbers of electrons  IONS Different numbers of neutrons  ISOTOPES Example: Hydrogen has 3 isotopes Hydrogen 1 Hydrogen 2 (deuterium) Hydrogen 3 (tritium)

THINK-PAIR-SHARE What do you think the following atoms look like? Number of protons, electrons, neutrons? Draw a model of each! Hydrogen 1 Hydrogen 2 (deuterium) Hydrogen 3 (tritium)

Isotopes are named by their Mass number. This isotope is Nitrogen 15 or Nitrogen-15

But look at your periodic table… The atomic mass of nitrogen is 14.01 amu. Rounding that to the nearest whole number, we see that the most common isotope of nitrogen is nitrogen-14. This example just happens to be talking about nitrogen-15.

Continue looking at your periodic table What is the most common isotope of Phosphorous? (round what you see on the periodic table) 31 amu (30.97 rounded to the nearest whole number) What is the most common isotope of Boron? 11 amu (10.81 rounded to the nearest whole number)

Use your periodic table to… Write symbols for the following: P B Remember, Mass Number = protons + neutrons Mass Number is a whole number

Atoms to Elements Let’s review: Each element or atom consists of a nucleus made up of protons and neutrons And electrons in shells or orbits around the nucleus The number of protons/electrons defines the element Elements can combine to form more complex stuff (compounds) Elements with different amounts of neutrons are isotopes

Atomic Mass Atomic Mass (or Atomic Weight) takes into account all the different isotopes Atomic Mass is an AVERAGE of all the different isotopes

Example Calculation A sample of silver is 51.35% silver-107 and 48.65% silver-108. What is its average atomic mass? Change the percents to decimals, multiply by the corresponding mass number, add results together. 0.5135 x 107 = 54.9445 0.4865 x 108 = 52.542 Total = 107.4865 amu = 107.49 amu (compare this to the decimal on your periodic table)

The next two slides go with compounds but have good pictures so I kept them in the presentation – don’t match unit 3 notes.

Atoms to Elements to Atomic Symbols + + Oxygen (O) Silicon (Si) Oxygen (O) = Quartz (SiO2)

Atoms to Elements to Atomic Symbols Galena (PbS) is not an element It is made up of more than one type of atom: Lead and Sulfur + = Sulfur Lead Galena