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Elements & Atoms SCA 7th Grade Science Mrs. Farrer Atoms of Ma*er •  Ma*er is anything that takes up space and has mass. •  All ma>er is made of atoms •  Atoms are the building blocks of ma>er, sort of how bricks are the building blocks of houses. An atom refresher •  An atom has three parts: •  Proton = posiEve •  Neutron = no charge •  Electron = negaEve •  The proton & neutron are found in the center of the atom, a place called the nucleus. •  The electrons orbit the nucleus in a cloud! Picture from http://education.jlab.org/qa/
atom_model_03.gif
What are elements? •  Elements are the alphabet to the language of molecules. •  To make molecules, you must have elements. (just as le)ers are to words) •  Elements are made of atoms. While the atoms may have different masses and organizaEon, they are all built in the same way. Information & picture from Chem4kids at
http://www.chem4kids.com/files/
atom_structure.html
Graphic from http://education.jlab.org/atomtour/fact2.html
# neutrons = Atomic Mass – Atomic #
How to interpret the Periodic Chart Atomic Number:
Number of protons
and it is also the
number of electrons
in an atom of an
element.
Elements
Name
8
O
Oxygen
16
Atomic Mass/Weight:
Number of protons +
neutrons.
Element’s
Symbol:
An abbreviation
for the element.
Subatomic Par7cles Par7cle
Electron
Proton
Neutron
Symbol e-­‐ Charge 1-­‐ Rela7ve Mass 0 p+ + 1 n
0 1 7
Loca7on of Subatomic Par7cles electrons 10-­‐13 cm protons nucleus
neutrons 10-­‐8 cm 8
Atomic Number Number of protons In the nucleus of an atom 9
Periodic Table l Represents physical and chemical behavior of elements l Arranges elements by increasing atomic number as you go across the period and down a group. l Repeats similar proper7es in columns known as chemical families or groups 10
All atoms of an element have the same number of protons 11 protons
Sodium
11
Na
11
Assessing Atomic Theory Knowledge State the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium
1) 137 protons 2) 81 protons 3) 56 protons 12
Solu7on AT 1 State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium
3) 56 protons LecturePLUS Timberlake
13
Number of Electrons l An atom is neutral l The net charge is zero l Number of protons = Number of electrons l Atomic number = Number of electrons 14
Mass Number Counts the number of protons and neutrons in an atom THERFORE Mass Number – Atomic # = # Neutrons 15
Atomic Symbols l Show the mass number and atomic number l Give the symbol of the element mass number 11
atomic number Na sodium-­‐23 23
LecturePLUS Timberlake
16
More Atomic Symbols 16 O 8 8 p+ 8 n 8 e-­‐ 31 P 15 15 p+ 16 n 15 e-­‐ 65 Zn 30 30 p+ 35 n 30 e-­‐ 17
Learning Check AT 3 An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom 1) 30 2) 35 3) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67 18
Learning Check AT 4 Write the atomic symbols for atoms with the following: A. 8 p+, 8 n, 8 e-­‐ ___________ B. 17p+, 20n, 17e-­‐
C. 47p+, 60 n, 47 e-­‐
___________ ___________ 19
Review of the Atomic Model •  Greek Philosophers – Democritus student of Leucipissus, -­‐ atomic theory of the universe •  Dalton late 1600s •  Thomson (chocolate chip cookie) •  Rutherford (peach) •  Bohr – solar system (onion) •  Cloud -­‐ Fan •  New Atomic Model (w/chadwick) – cloud with neutrons and protons in the nucleus. Atom Models to be used for electronic studies •  There are two models of the atoms we will be using in class. –  Bohr Model –  Lewis Dot Structure Bohr Model •  The Bohr Model shows all of the parEcles in the atom. •  In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P wri>en on them. Neutrons should be blank or have an N. •  In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. +
Positive
Neutral
Electrons have special rules…. •  You can’t just shove all of the electrons into the first orbit of an electron. •  Electrons live in something called shells or energy levels. •  Only so many can be in any certain shell. BUT HOW YOU ASK??? THE SHELLS…. Nucleus
1st shell
2nd shell
3rd shell
Adapted from http://www.sciencespot.net/Media/
atomsfam.pdf
The HOW!!! •  How to draw a Lithium atom •  First, look at the Periodic Table •  Second, determine the number of protons (Look @ the atomic number) •  Then determine the number of neutrons (Atomic mass – atomic number) •  Then determine the number of electrons (Look @ the atomic number) 3
Li
Lithium
7
So let’s try it…. Atomic Number =
Protons = 3
3
-
Li
+
+
+
-
-
Lithium
7
•  Electrons = # of Protons = 3
•  2 in the 1st shell
•  1 in the 2nd shell (valence
electron)
Atomic Mass # N + # P
Neutrons = 7 – 3 = 4
Lewis Dot Structure •  The Lewis dot structure is a bit different from the Bohr model. •  It only shows the element symbol and it’s outer most electron shell. -
-
-
+
+ + +
-
-
+ + +
+
-
-
•
• O ••
••
-
How to… 1.  Write the symbol. 2.  Start on the right hand side, working your way clockwise around the symbol. 3.  Try Lithium HERE IS A YOU TUBE VIDEO to watch if you desire!! h>ps://www.youtube.com/watch?v=y6QZRBIO0-­‐o Your acEvity… •  Beans as subatomic par7cles –  LenEls are electrons –  Lima Beans are protons –  Kidney beans are neutrons •  Fold a paper – 
– 
– 
– 
hamburg half then half again. Open paper and do a hot dog fold. Draw lines on all folds. Label each rectangle with an element in order of increasing Atomic # (name an Symbol) •  Create a Bohr model for Li, Be, B, C, N, O, F,& Ne –  Draw on paper with protons and Neutrons on the nucleus and electrons on the correct orbitals –  Draw the Electron Dot structure under the Bohr model –  Write the word valence and give the number of valence electrons (# of electrons in the outermost orbital or the number of electrons on the dot structure!