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The Chemistry of Life.

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Presentation on theme: "The Chemistry of Life."— Presentation transcript:

1 The Chemistry of Life

2 Elements A substance that cannot be broken down into simpler chemical substances. Identified by a one or two letter symbol C = carbon, O= oxygen, H =hydrogen, Na = sodium

3 Atom The smallest particle of an element that has the characteristics of that element

4 The Structure of an Atom
Nucleus: the center of the atom with an overall positive charge (+) Made up of: Protons: positively charged particles (+) Neutrons: particles that have no charge Electron Cloud: made up of electrons: negatively charged particles (-) Electrons are orbiting the nucleus and moving very quickly. Electrons form bonds with other elements.

5 - + Particle Charge Location Proton Nucleus Neutron nucleus Electron
No charge nucleus Electron - Outside the nucleus


7 Electrons move in energy levels: certain regions around the nucleus can hold a limited number of electrons 1st level – maximum of 2 electrons 2nd level – maximum of 8 electrons 3rd level – maximum of 18 electrons Outer most energy level (orbit) likes to be full - more stable Atoms will give up, gain, or share electrons to fill the outer orbit

8 Valence electrons The electrons in the outer most energy level involved in the bonding of two atoms.

9 Sodium – 11 protons and 11 electrons
2 electrons in the 1st level 8 electrons in the 2nd 1 electron in the 3rd Sodium has 1 valence electron

10 Periodic Table of Elements
A reference table of the elements arranged in order of increasing atomic number. Atomic number: number of protons in the nucleus of an atom Identifies the element Equal to the number of electrons (in a neutral atom) Atomic mass: the average of all the isotopes of an element -isotope: atoms of the same element that have different numbers of neutrons.

11 Atomic Number Symbol Name of the Element Atomic Mass

12 To determine the number of neutrons in an atom:
Mass Number – Atomic Number = # of Neutrons. 3 Li Lithium 6.941 Example: Lithium has an atomic number of 3 and a mass number of which we round to 7. Mass Number – Atomic Number = # of Neutrons = 4 Neutrons Therefore…. Lithium has: protons and 4 neutrons What about electrons?????? Remember: neutral atoms (atoms with no charge) have an equal number of protons and electrons…… Therefore..... Lithium has: 3 electrons.

13 Fill in the chart below using the Periodic Table
Element Sym Atomic # Mass Protons Electrons Neutrons Val. e Sodium Carbon Nitrogen Oxygen Hydrogen Potassium


15 Groups: the elements in a column
Elements have similar characteristics Elements have the same number of valence electrons Periods: horizontal row across the table Elements have different properties

16 Bohr Model A model used to show energy levels and where electrons may be located around the nucleus. The energy level closest to the nucleus holds 2 electrons The next energy level holds 8 electrons. The third energy level can hold up to 18 electrons. The last energy level holds electrons called valence electrons

17 To Draw a Bohr Diagram: Find your element on the periodic table.
Inside the nucleus write the number of protons and number of neutrons (determine by substracting atomic number and atomic mass.) Determine the number of electrons – it is the same as the atomic number. This is how many electrons you will draw.

18 Carbon has an atomic number of 6
You will draw 6 electrons. Remember your rules, the first shell can only have2 electrons. The remaining 4 electrons will go into the next energy level. 6 P 6 N

19 Lewis Structures/Electron Dot Diagram
Find your element on the periodic table. Determine the number of valence electrons. This is how many electrons you will draw.

20 Lewis Structures Find out which group (column) your element is in.
This will tell you the number of valence electrons your element has. You will only draw the valence electrons.

21 Groups Group 13 = 3 ve Group 14 = 4 ve Group 15 = 5 ve
(except He) Group 1 = 1 electron Group 2 = 2 electrons

22 C Lewis Structures/EDD Write the element symbol.
Carbon is in the 14th group, so it has 4 valence electrons. Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol. C

23 C Lewis Structures/EDD Check your work.
Using your periodic table, check that Carbon is in the 14th group. You should have 4 total electrons, or dots, drawn in for Carbon. C

24 Li Ne Mg Cl

25 Compounds A substance that is composed of atoms of two or more different elements that are chemically combined. - ie. Water, glucose, salt, carbon dioxide

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