atomic nature of matter · molecules • atoms combine to form molecules. • can be simple or...
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![Page 1: Atomic Nature of Matter · Molecules • Atoms combine to form molecules. • Can be simple or complex combinations – Simple: 2 hydrogen atoms and 1 oxygen atom combine to form](https://reader033.vdocuments.site/reader033/viewer/2022043022/5f3df49b31613e14314b99c5/html5/thumbnails/1.jpg)
Atomic Nature of Matter Objectives: 1. Define the atom and parts of the atom 2. Define the properties of an atom;
molecules, compounds; states of matter
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Atoms
• Atoms are the building blocks of matter. • Matter – any thing that has mass and takes up
space. • There are approximately 112 types of atom
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Atoms (cont) • The smallness of an atom
– 1 drop of water contains about 1023 atoms . • Atoms are ageless
– All atoms on Earth originated in the deep interiors of ancient stars
• Atoms are recyclable – Atoms cycle from one object to
another – We do not own the atoms, we borrow them
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Elements
• class of identical atoms • Living things are composed of about 5 elements
1. oxygen (O) 2. carbon (C) 3. hydrogen (H) 4. nitrogen (N) 5. calcium (Ca)
• Everyday materials are composed of about 14 elements
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Molecules • Atoms combine to form molecules. • Can be simple or complex combinations
– Simple: 2 hydrogen atoms and 1 oxygen atom combine to form water – Complex: DNA ( the blue print of life!)
• Most molecules are too small to be seen • Macromolecule can be seen
– A diamond is a macromolecule
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Compounds
• Chemical reaction – process in which atoms rearrange to form different molecules/compounds
• Compound - Substance that is made from atoms of different elements combined in fixed proportions.
• Chemical formula - tells us the proportion of each kind of atom. – Examples: CO2, NaCl
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Compounds (continued)
• Have different properties from the elements they are made from. – NaCl (table salt): Sodium is explosive in water
and chlorine is a poisonous gas. – H2O (water): at room temperature, hydrogen and
oxygen are gases but water is a liquid
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The Atomic Nucleus
• central region of the atom where most of the mass is.
• Discovered by Ernest Rutherford – gold foil experiment (1910)
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Rutherford’s Experiment • Shot Alpha particles at gold foil
– Alpha particles - positively charged pieces given off by uranium
• When the alpha particles hit a fluorescent screen, the screen glows.
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Lead block
Uranium
Gold Foil
Fluorescent Screen
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He expected the particles to pass through
He thought all of the mass of an atom was evenly distributed.
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What happened?
Particles deflected in all directions
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How he explained it
+
Atom is mostly empty Small dense, positive piece at center
Alpha particles are deflected by it if they get close enough because they are positive
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Atomic Nucleus
• Atoms are classified by their atomic number. (the number of protons in the nucleus)
• Nucleus contains protons and neutrons. • The number of protons define the element.
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Electrons in the Atom
• Atoms are neutral – The number of electrons = the number of protons – When not equal, you have an ion not an atom. – Arrangement of electrons dictates how atoms
combine to form molecules
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• Chart that lists atoms by their atomic number and by their electron arrangements.
• Elements arranged so chemical and physical properties have trends following a pattern of repetition.
Periodic Table of the Elements
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States of Matter
• 4 states of matter – Solid – Liquid – Gas – Plasma
• All substances can be transformed from one state to another
• Changes of state are caused by changing energy which affects the temperature
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Atoms in Constant Motion • Solids – atoms and molecules vibrate around fixed
positions. • Liquids - molecular vibration increases and material
takes the shape of their container. • Gases –molecules gain more energy, they break away
from each other. • Plasma – electrons shake loose of atoms results in
free electrons and positive ions.