Ch 11 Introduction to Atoms

1. Ch 11Introduction to Atoms

2. 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’sidea. He believed that ___________________________________ • Who was correct? Aristotle or Democritus??

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

4. 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.

5. 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)

6. 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 _______.

7. 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 _________________.)

8. 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 ______.

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

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

11. 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 ___________.

12. 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 ______ __________.

13. 4.2 The Atom • How small is an _____? • 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 _________)

14. 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 ______________

15. 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.

16. 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.

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

18. HOW DO ATOMS OF DIFFERENT ELEMENTS DIFFER?

19. 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:

20. 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 -

21. 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

22. 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.

23. 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

24. 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