Concept Summary Batesville High School Science

Atoms  Atoms are the building blocks of matter.  Anything that takes up space is made of atoms.

Kinds of Atoms  There are about 110 different kinds of atoms.  About 90 kinds of atoms occur naturally.  About 20 kinds of atoms occur only in the laboratory.

Elements  Each kind of atom is called an element.  Each element has a name and a symbol.

Kinds of Atoms  About 90% of the atoms in the universe are the lightest element, hydrogen, (H).  Most of the rest of the atoms in the universe are the next lightest element, helium (He).  The 88 other natural elements are relatively rare in the universe.

Your Atoms  Living things are made mostly of:  Carbon (C)  Oxygen (O)  Hydrogen (H)  Nitrogen (N)  Calcium (Ca)

The Atmosphere  The Earth’s atmosphere is about 80% nitrogen (N).  Most of the rest of the atmosphere is oxygen (O)

Atoms Are Recyclable  Atoms are almost indestructible.  The atoms in your body were once part of other matter.  When you die, your atoms are not destroyed - they become part of something else.  Atoms can combine and recombine with other atoms.

Atoms are Recyclable  Atoms heavier that helium (He) were probably made in intense stellar explosions called supernova.  Elements can be converted to other elements by radioactive processes.

Atoms are Small  1 gram of water contains about atoms (100,000,000,000,000,000,000,000)  There are more atoms in your lungs right now than there are breathfulls of air in the atmosphere.  Atoms cannot be seen - even with the most powerful microscope.

Atoms Move  All atoms are in constant motion.  In solids, atoms mostly vibrate in place.  In liquids, atoms are somewhat free to move about.  In gasses, atoms are almost completely free to move about.

Evidence for Atoms  Brownian motion - “jiggling” of microscopic pollen grains in water  Discovered in 1827 by Robert Brown  Explained in 1905 by Albert Einstein  Electron Microscope (1970s)  Scanning Tunneling Electron Microscope (1980s)

Molecules  Atoms can combine to form molecules.  Molecules can contain from two to many thousands of atoms.  Two oxygen atoms like to combine to form an oxygen molecule (O 2 )  Water is made of two hydrogen atoms and one oxygen atom (H 2 O)  DNA is a huge, helix-shaped molecule.

Compounds  Molecules composed of atoms of different types are called compounds.  Water (H 2 O)  Carbon dioxide (CO 2 )  Salt (NaCl)  The combination of symbols H 2 O is a chemical formula.

The Atomic Nucleus  Almost all of the mass of an atom is concentrated in a tiny central region called the nucleus.  Discovered in 1911 by Ernest Rutherford  The nucleus is less than a trillionth of the volume of an atom.

What’s in a Nucleus?  The nucleus has 2 primary building blocks:  Protons - positive electric charge  Neutrons - electrically neutral  Protons and neutrons have approximately the same mass  Protons and neutrons are called nucleons.

Atomic Number  The number of protons in an atom’s nucleus determines the type of atom (element) it is.  1 proton = hydrogen  2 protons = helium  6 protons = carbon  8 protons = oxygen  The number of protons in an atom is the atomic number of the atom.

Isotopes  An isotope of an element has the same number of protons, but a different number of neutrons.  Helium = 2 protons + 2 neutrons  Isotope of Helium = 2 protons + 1 neutron

The Rest of the Atom  Outside the nucleus, the atom is almost completely empty.  Electrons (negative charge) orbit the nucleus.  Electrons have about 1/2000 the mass of protons and neutrons.

Electrons & Ions  Normal atoms have the same number of electrons and protons.  Electrons are arranged in “shells” in the atom.  An ion is an atom with too many electrons (negative ion) or too few electrons (positive ion)

The Periodic Table  The Periodic Table of the Elements lists atoms by atomic number and electron arrangement.  Element to the right has one more proton  Element below has one more electron shell  Elements in a column are a group - they have similar chemical characteristics.

Phases of Matter  Solid  Atoms held in place by other atoms  Atoms can vibrate in place.  Liquid  Atoms are free to slide over other atoms  Gas  Atoms are completely free to move about.  Plasma  Positive ions and free electrons  No complete atoms  Most common form in the universe

The End