Ch 11 Introduction to Atoms

The Beginning of Atomic Theory Democritus & Aristotle Can you cut a piece of paper in half and cut those halves in half and continue until you are left with 1 particle?   If you could do this you would end up with what Democritus called an _________= ______________________ Aristotle _____________ with democritus’s idea. He believed that ___________________________________ Who was correct? Aristotle or Democritus??

The Beginning of Atomic Theory ____________________was correct! Matter is made of particles which we call ___________.   Atom -

The Beginning of Atomic Theory Dalton – 1803 Dalton’s atomic theory was based on _________________! All substances are made of ______ Atoms are small particles that cannot be _____, _______, or _________. Atoms of the same element are _________ and atoms of different elements are _________. Atoms join with other atoms to make _____ substances.

The Beginning of Atomic Theory New information didn’t quite fit with _______ ideas. His atomic theory had to be _________. Thomson- 1897 Discovered the ____________ charged particles There are __________ inside the atom. Atoms can be broken down further. (Dalton thought atoms were solid spheres – so he’s wrong)

CATHODE-RAY TUBE A positively charged plate was attracted to a ______. Therefore, the beam must be made up of ________ charges. Thomson concluded these negative charges are _______ in every kind of _______.

The Beginning of Atomic Theory ________- A subatomic particle that has a negative charge. Thomson described his model of the atom like plum pudding. Today you might call it the ______________ _____ model. (with electrons represented by _________________.)

The Beginning of Atomic Theory Rutherford- 1909 Rutherford was a _____________ of Thomson’s. He tried to help prove Thomson theory was _______ and ended up proving him ______! He aimed a beam of small, _________________ (α particles) at a thin piece of gold foil. Photo paper behind the gold recorded where the charged particles hit. Surprising Results He thought the particles would _______________ the gold in a straight line. Some particles were ________. Some shot right ______.

Rutherford’s Gold-Foil Experiment Rutherford determined an atom must be mostly ______ ______ with a tiny part made of highly dense material.

Rutherford’s Model ________ – The centrally located, tiny, extremely dense positively charged part of an atom.

The Beginning of Atomic Theory Bohr – 1913 Niels Bohr proposed that electrons move around the nucleus in _______________________________. Electrons can jump from path to path but cannot exist in _____________ paths. Think of ________ on a ladder. You can stand on the rungs, but not ________ the rungs. Or think of planets in our solar system – they do not stray off the set path or ___________.

The Modern Atomic Theory Schrӧdinger and Heisenberg Electrons ________ travel in definite paths as Bohr suggested. The exact path of the electron ______ be predicted. There are regions where it is likely to be found called ______ __________.

4.2 The Atom How small is an _____? The Nucleus A penny contains __________ atoms. (20,000,000,000,000,000,000,000 atoms) An atom is made up of _______, _______, and _________. The Nucleus Protons – The mass of protons are measured in atomic mass units (amu). Each proton has a mass of __________ _________- Particles in the nucleus that have ___ electrical charge. Neutrons have a mass of 1 amu. (Same as _________)

The Atom Outside the nucleus _________ are found outside the nucleus. They have a _______ charge. They have a mass of almost _____. If the number of protons __________ the number of electrons, the atom is ______________

HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER? Atoms of different elements have different numbers of ____________. No two elements have the same _____________. Atomic number is the number of ________ in an atom. All atoms of the _____________ have the _________ atomic number.

HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER? So how do we figure out the number of neutrons for an atom? The number of _____________ = the number of _______________ Mass number – The mass number does not include the mass of ____________ because they are so ___________and have very little effect.

HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER? Where do you find these numbers?  On the ____________________ ! C C C     # of neutrons = _________ - _________ # of neutrons in C = ____ - ____ C P+ = No= E- = ______ # __ + # __ ___ ______ # __ ___

HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER? Mass # Atomic # Protons Neutrons Electrons Li Be B C N O F Na k

DRAWING BOHR MODELS OF ATOMS Draw the nucleus and label with #p & #n Draw electron orbitals 1st orbital can have ______ electrons only 2nd and 3rd ring can each have ______electrons Fill – _____________________ Inner rings must be filled first before any electron enters a higher ring!!!!! Examples:

Changing Atoms If you change a persons hair color does it change who they are? Weight? What subatomic particle determines an atoms identity?___________ Therefore, the number of electrons and neutrons can change in the atom and it is still the same atom. If the number of protons __________ the number of electrons, the atom is ______________ If the number of protons ___________ the number of electrons, the atom becomes charged and we call it an _______.  Positively charged ions – Negatively charged ions -

ISOTOPES _________- Atoms that have the same number of protons, but have different numbers of neutrons. Examples: Hydrogen -1 and Hydrogen -2 Naming Isotopes Write the __________ of the element, followed by a hyphened and the _____________________ of the isotope. Ex. A hydrogen atom with 1 proton and 0 neutrons A hydrogen atom with 1 proton and 1 neutron

ISOTOPES Mass Number – The sum of the _________________ in an atom. (__________ are not included.) Mass # = protons + neutrons Atomic Mass – The _____________ of the masses of all the ___________ occurring isotopes of that element.

Solving the Atomic Mass Ex: Skittles consist of Orange – 1 which is 25% of the Skittles and Red – 2 which is 75% of skittles. Step1: change percents to decimals. Step 2: multiply the decimal by the mass Step 3: add the two answers together

Solving for Atomic Mass Ex: Chlorine-35 which is 76% of the Chlorine atoms and Chlorine-37 which is 24% of Chlorine atoms. Step1: change percents to decimals. Step 2: multiply the decimal by the mass Step 3: add the two answers together