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Chapter 4. 4.1 Atoms Democritus (460 BC – 370 BC) first suggested the idea of atoms Indivisible and indestructible.

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Presentation on theme: "Chapter 4. 4.1 Atoms Democritus (460 BC – 370 BC) first suggested the idea of atoms Indivisible and indestructible."— Presentation transcript:

1 Chapter 4

2 4.1 Atoms Democritus (460 BC – 370 BC) first suggested the idea of atoms Indivisible and indestructible

3 Atoms The first model of the atoms was Daltons All mater is made up of individual particles, which are indivisible

4 Daltons Atomic Theory 1. All matter is made of atoms. Atoms are indivisible and indestructible.

5 Daltons Atomic Theory 2. All atoms of a given element are identical in mass and properties

6 Daltons Atomic Theory 3. Compounds are formed by a combination of two or more different kinds of atoms.

7 Daltons Atomic Theory 4. A chemical reaction is a rearrangement of atoms

8 Thomsons Model Discovered electrons Often called the Plum-Pudding Model No mention of amount of electrons or their arrangement around the nucleus Revised Daltons theory to account for subatomic particles

9 Rutherford Model Discovered nucleus All of an atoms positive charge is concentrated in its nucleus Electrons surround a dense nucleus Rest of the atom is empty space

10 Rutherford Model Known as the nuclear model The protons are located in the nucleus The electrons are around the nucleus The electrons occupy most of the volume of the nucleus

11 The Atom The smallest part of an element VERY SMALL

12 Atomic Structure Atoms can be broken down Protons Neutrons Electrons Every Element is different based on the number of each (individual personality)

13 Protons (p + ) Positively Charged Each has a +1 charge

14 Electrons (e - ) Negatively charged Each has a -1 charge

15 Neutrons (n 0 ) No charge or neutral Mass = mass of proton

16 The Atomic Nucleus The central core of an atom Made of p + and n 0 Most of the mass, little volume Nucleus has a positive charge

17 The Atomic Nucleus Electrons orbit around nucleus like planets in the solar system Called the electron cloud Very little mass, lots of volume

18 How do we know the number of each elements p +, e -, n 0 Periodic Table is arranged by the elements numbers

19 H Nuclear Symbol Hydrogen Name of Element Atomic Number Mass Number (round to the nearest whole number)

20 Atomic Number Amount of protons from one element to the next Ex: Oxygen atomic number = 8 because it has 8 protons

21 Atomic Number Since all elements start off as neutral …. The number of protons = number of electrons!

22 Mass Number Mass Number = protons + neutrons

23 Composition of an Element Use atomic number and mass number to determine composition # p + = atomic # # e - = atomic # # n 0 = mass # – atomic #

24 What can change in an atom Protons: can never change Electrons: if the number changes, then an ion is formed Neutrons: If the number changes, then an isotope is formed

25 IF the proton number changes… Then you have an entirely different atom

26 If the neutron number changes… Called an Isotope Mass number changes

27 If an atom gains electrons, then… The atom becomes negatively charged If an atom loses an electron, then… It becomes positively charged

28 Isotopes of Elements Protons never change, but the number of neutrons may vary

29 Isotopes Isotopes of the same element are the same except for # of n 0 # of n 0 vary so mass number changes

30 Isotopes Carbon-12, Carbon-14, Carbon-16 How many protons in each version of carbon? How many neutrons in each version of carbon?

31 Hydrogen Hydrogen has three known isotopes Hydrogen-1 (one proton, no neutrons) Hydrogen-2 (one proton, 1 neutron) Hydrogen-3 (one proton, 2 neutron)

32 4.3 Bohrs Model Electrons arranged in circular paths around nucleus Orbit like planets n = energy level Only a certain amount of electrons can fit in each energy level

33 Bohrs Model Electrons are located in energy levels with a fixed amount of energy

34 Energy Levels Each energy level can only hold 2 electrons Each energy level has X number of orbitals that can hold 2 electrons each Pauli Exclusion Principle Each orbital holds 2 electrons that spin in opposite directions

35 Energy Levels How many electrons fit in the 1 st, 2 nd, 3 rd and 4 th energy levels? Energy LevelNumber of Orbitals Maximum number of Electrons

36 Hunds Rule When electrons occupy orbitals, one electron enters each orbital until all orbitals contain their max amount

37 Hunds Rule Partially filled orbitals are much more stable than empty orbitals Example: Carbon has 6e - has 2e - in first orbital has 4e - in second orbital

38 Orbitals simplified Each energy level can hold 8 electrons except the first which holds 2 Fill in each level until

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