BellRinger:
Choose any element from the periodic table and draw that square exactly as it appears in the periodic table.
Matter is anything that occupies space and has mass.
Think Pair Share:
What is the difference between mass and weight?
Mass is the quantity of matter
Weight is the force of gravity acting on mass.
Elements are substances that cannot be broken down into simpler kinds of matter.
The smallest particle of an element that retains the properties of the element is an atom.
Charge
Proton
Neutron
Electron
Location
Elements are substances that cannot be broken down into simpler kinds of matter.
All of the known elements are organized into the Periodic table of elements.
=
also = number of electrons
= protons + neutrons
In atoms, the number of positively charged protons is balanced out by an equal number of negatively charged electrons.
How many protons?
6
How many electrons?
6
How many neutrons?
6
Atomic Symbol
Atomic Mass
Protons and neutrons are located in the nucleus of the atom.
What element is this?
Electrons move around the nucleus and are arranged in orbitals.
Compounds are made up of atoms of two or more elements.
NaCl
H 20
The smallest unit of a compound is a molecule.
Atoms in a compound can be help together by covalent bonds or ionic bonds.
In covalent bonds, atoms share electrons.
In ionic bonds, electrons are transferred from one atom to the other.
Ioninc bonding in NaCl
An element that gains or loses an electron is called an ion.
BellRinger:
Three people per table, only your notebooks on the table.
Covalent bonding in H2O
BellRinger: Draw covalent bonding in a water molecule.
Covalent bonding in H2O
In a water molecule, electrons are shared, but they are not shared equally. The electrons spend more time with the oxygen atom than they do with the hydrogen atom.
This means that water is a polar molecule.
Polar molecules have an uneven distribution of charge, meaning a positive side and a negative side.
Compare this to a molecule of the compound methane (CH4).
Methane is nonpolar.
Polar substances can only dissolve other polar substances.
To observe this:
1.Fill your test tube halfway with water.
2. Put one squirt of oil into the test tube with the large pipette.
3. Put the cap on the test tube and lightly shake.
4. Record your observations in the notebook and explain why the water behaved this way.
Because water is a polar molecule. There is a force of attraction between the postive (hydrogen) side of one water molecule to the negative (oxygen) side of another water molecule.
This called a hydrogen bond.
This causes water molecules to have a force called cohesion.
Cohesion holds molecules of a single substance together.
Lets observe cohesion:
Put a couple of small drops of water on your wax paper.
Do the molecules spread out or stick together?
Now use your pipette to move these drops of water as close as you can to each other without them touching.
What happens when they get close to each other?
Lets observe cohesion:
Predict how many drops of water you can fit on top of your coin. Record that prediction in your notebook.
Now, put water into your beaker and using the pipette, carefully put as many drops of water on top of the coin as you can. Count the drops.
Did you fit more or less drops on the coin than you predicted? Why were so many drops able to fit on top of the coin??
Lets observe cohesion:
Try to float a paperclip on top of the water in your beaker.
Record and explain your observations.
Because of these hydrogen bonds, water is less dense as a solid than it is as a liquid.
Water is very unique in this regard. Other substances are more dense as a solid.
Short Essay: Why is this density property of water important to life?
Atom
Molecule
Covalent Bond
Element