Matter & The Atom

Matter The term matter describes all of the physical substances around us Matter is anything that has mass and takes up space The Universe is made up of matter and energy

Matter is made up of atoms. *An atom is the smallest whole particle of matter. * *Matter is made up of atoms. *An atom is the smallest whole particle of matter. *

Sub-Atomic particles are smaller than atoms and are the tiny particles that an atom is made of. * Sub-Atomic particles are smaller than atoms and are the tiny particles that an atom is made of.

Early Models of the Atom Rutherford Mostly empty space Small, positive nucleus Contained protons Negative electrons scattered around the outside

Early Models of the Atom Bohr Electrons move in definite orbits around the nucleus

Modern Model of the Atom Modern Model of the Atom The electron cloud Sometimes called the wave model Spherical cloud of varying density Varying density shows where an electron is more or less likely to be

4 Atomic Structures Nucleus – Protons – Neutrons Electrons

nucleus nucleus ATOM + N N proton Electron ctron ele Electron ctron neutron Neutron What do these particles consist of? Proton Electron Cloud

Atomic Structure Electrons Tiny, very light particles Have a negative electrical charge (-) e- Move around the outside of the nucleus

Atomic Structure Protons Much larger and heavier than electrons Protons have a positive charge (+) Located in the nucleus of the atom Located in the nucleus of the atom

Atomic Structure Neutrons Large and heavy like protons Neutrons have no electrical charge Located in the nucleus of the atom Located in the nucleus of the atom

Atomic Mass Unit or AMU Protons, neutrons and electrons have certain mass But it is extremely small mass Study the table on next slide……

Atomic StructureParticleSymbolCharge Relative Mass Actual Mass (g) ProtonP+P x NeutronN0N x Electrone-1/ x

Atomic Structure

Describing Atoms Atomic Number Atomic Number Atomic Number = number of protons In a neutral atom, the # of protons = the # of electrons = the # of electrons

Describing Atoms Atomic Mass Atomic Mass Atomic Mass = the number of Atomic Mass = the number of protons + neutrons protons + neutrons That ’ s basically the mass That ’ s basically the mass of the nucleus of the nucleus

Atomic Number and Number of Protons The atomic number of sulfur (S) is 16. A. The atomic number of sulfur (S) is 16. Sulfur has 16 protons in its nucleus Sulfur has 16 protons in its nucleus B. The atomic number of iron (Fe) is 26. Iron has 26 protons in its nucleus C. The atomic number of silver (Ag) is 47. Silver has 47 protons in its nucleus Silver has 47 protons in its nucleus Q 7

Q 12 Mass Number or Atomic mass Atomic Number Element Name 4 Facts about each Element In the element box Element Symbol

Q 12 B Boron Can you name this Element? Atomic Number Atomic Symbol Atomic Name Atomic Mass or Mass Number

Can you name this Element? Selenium Se

Q Carbon C Can you name this Element?

Q 12 K Potassium Can you name this Element?

EXAMPLE How many protons and electrons are found in this atom? Cs Atomic number = # of protons = # of electrons There are 55 protons and 55 electrons Q 13

EXAMPLE How many neutrons are in this a element? Cs Q 13 Mass number = # of protons + # of neutrons 133 – 55(protons) = 78 There are 78 neutrons

H Hydrogen 1 1 Protons: 1 Neutrons: 0 Electrons: 1 Q 14 How many protons, neutrons and electrons does Hydrogen have? Which element is this?

Na Sodium Protons: 11 Neutrons: 12 Electrons: 11 Q 15 Which element is this? How many protons, neutrons and electrons does Sodium have?

Ions An atom that carries an electrical charge is called an ion Ion can have either a positive or negative charge negative charge It depends whether the atom gains or loses electrons

Ions The number of protons does not change in an ion. The number of neutrons does not change in an ion. So, both the atomic number and the atomic mass remain the same.

Ions If the atom gains electrons, the atom becomes negatively charged Why? Because there are more negative charges (e-) than positive charges or protons (+)

Ions If the atom loses electrons, the atom becomes positively charged WHY? WHY? Because the number of positively charged protons will be higher than the number of negatively charged electrons

Positive Ions An atom that has lost an electron. Now it has one more proton than electron. One more proton means one more positive charge. This makes the total charge of the atom POSITIVE.

Negative Ion An atom has gained an electron. Now it has one less proton than electron. One less proton means one less positive charge. This makes the total charge of the atom NEGATIVE.

Isotopes The number of protons for a given atom never changes. The number of neutrons can change. The number of neutrons can change. Two atoms with different numbers of neutrons are called isotopes Isotopes have the same atomic # Isotopes have different atomic Mass # ’ s

Rhenium in natural state Re Protons: 75 Neutrons: 111 Electrons: 75 Q 16

Rhenium isotope Re Protons: 75 Neutrons: 112 Electrons: 75 Q 17 What has changed in the Isotope?

Rhenium Rhenium isotope Re What has changed in the Isotope? T he Atomic mass increased from 186 to 187…Why? T he number of neutrons increased by 1 from 111 to 112, so…… (protons) = 187 (Atomic mass)

Hydrogen Isotopes