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Chapter 4 Pg. 100-118. Ancient Greek Models of Atoms __________- – thought that all substances were built up from only ____ elements: earth, air, fire,

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Presentation on theme: "Chapter 4 Pg. 100-118. Ancient Greek Models of Atoms __________- – thought that all substances were built up from only ____ elements: earth, air, fire,"— Presentation transcript:

1 Chapter 4 Pg

2 Ancient Greek Models of Atoms __________- – thought that all substances were built up from only ____ elements: earth, air, fire, and water – matter could be divided an unlimited number of times __________- – believed that all matter consisted of extremely _____ particles that could not be divided – called particles atoms from the Greek word ________, which means “uncut” or “indivisible”

3 Dalton’s Atomic Theory ____________- born in England in 1766 – Teacher – Interest in predicting the _______, led to his study of the behavior of gases in air -- Correctly concluded that a gas consists of _________ _________

4 Dalton’s Atomic Theory Evidence for Atoms – Measured the ______ of elements that combine when compounds form. – Noticed that no matter how _______ or _____the sample, the ratio of the masses of the elements in the compound is always the same (aka fixed composition)

5 Dalton’s Atomic Theory ________ Theory- Dalton proposed the theory that all matter is made up of individual particles called ______, which cannot be divided. Main Points of Theory 1.All elements are composed of ______. 2.All atoms of the same element have the same mass, and atoms of ________ elements have different masses.

6 Dalton’s Atomic Theory Main Points of Theory continued… 3.__________ contain atoms of more than one element. 4.In a particular compound, atoms of different elements always combine in the _____ _____ Not all of Dalton’s ideas about atoms were completely ______, but scientists did not discard his theory, they revised it to take into account new discoveries

7 Dalton’s Atomic Theory

8 Thomson’s Model of the Atom When rubbed, some materials gain the ability to ______ or _____other materials. Based on their ________, they are said to have either positive or negative electric charges. Objects with ___ charges repel or push apart.

9 Thomson’s Model of the Atom Objects with ________ charges attract, or pull together. Some charged particles can flow from one location to another. A flow of charged particles is called an ________ _______

10 Thomson’s Model of the Atom J.J Thomson used _______ current to learn more about atoms

11 Thomson’s Model of the Atom Thomson’s Experiment (pg. 102) – __________ that the beam was a stream of charged particles that interacted with the air in the tube and cause the air to glow. – Placed charged _____ plates at either end-> caused beam to deflect or bend – Observed beam: ________ by negatively charged plate and attracted by positively charged plate

12 Thomson’s Model of the Atom Evidence for Subatomic Particles – Concluded that the particles in the beam had a _________ charge because they were attracted to the positive plate. – Thomson’s experiments provided the _____ evidence that atoms are made of even ______ particles. – Revised Dalton’s model to account for the ________ particles

13 Thomson’s Model of the Atom Thomson’s Model – Atom is ______: meaning it has neither a negative nor a positive charge – Negative charges were evenly ________ throughout an atom filled with a positively charged mass of matter – “______ _______” model (may want to think of chocolate chip ice cream)

14 Thomson’s Plum Pudding Model

15 Rutherford’s Atomic Theory _____, Rutherford discovered that uranium emits fast- moving particles that have a positive charge called _____ ________

16 Rutherford’s Atomic Theory Hypothesis: (asked student- _______, to find out what happens to alpha particles when they pass through a thin sheet of gold) Predicted that most particles would travel in a _______ path from their source to a screen that lit up when struck.

17 The _______ ______ Experiment – Aimed narrow beam of alpha particles at gold, the material around the ______ produced a flash of light when struck by fast-moving alpha particles – Could figure out ____ of alpha particles by observing the flash after they had passed through the gold – Did _____ support Rutherford’s prediction Rutherford’s Atomic Theory

18 Gold Foil Experiment continued… – More particles were deflected than he expected – About 1 out of every ______ was deflected by more than 90 degrees – Some alpha particles behaved as though they had struck an object and bounced _______ back Rutherford’s Atomic Theory

19 Gold Foil Experiment

20 Rutherford’s Atomic Theory Discovery of the Nucleus – Alpha particles whose paths were ________ must have come close to another charged object – The closer they came, the greater the deflection – _________: the positive charge of an atom is not evenly spread throughout the atom, it is concentrated in a very small central area- ______ – Nucleus: a dense, positively charged mass located in the center of the atom

21 Rutherford’s Atomic Theory According to Rutherford’s model, all of an atom’s _______ charge is concentrated in its nucleus

22 Chapter 4 Section 2 Pg

23 Properties of Subatomic Particles Protons, electrons, and neutrons are _________ particles Protons: – A __________charged subatomic particle that is found in the nucleus of an atom – Positive charge (amount varies among elements), each proton is _____ – Each _________ must contain at least one particle with a positive charge

24 Properties of Subatomic Particles Electrons – Comes from Greek word meaning “______” – A _________ charged subatomic particle that is found in the space outside the nucleus – Each electron has a charge ____

25 Properties of Subatomic Particles Neutrons – 1932, English physicist J. _________ designed an experiment to show that neutrons exist; concluded particles were ________ because a charged object did not deflect their path – A neutral subatomic particle that is found in the nucleus of an atom – ______ is almost exactly equal to that of a proton

26 Comparing Subatomic Particles Protons, electrons, and neutrons can be distinguished by _____, charge, and location in an atom. Protons and neutrons have almost the _____ mass It would take about 2,000 electrons to equal the mass of one proton Protons and neutrons are _______ nucleus, electrons are in outside space

27 Atomic Number and Mass Number ______ predicted that the atoms of any element are different from the atoms of all other elements Atomic Number – atoms of any given element always have the same number of protons – Atomic number of an _______ equals the number of protons in an atom of that element – _______ of different elements have different numbers of protons

28 Atomic Number and Mass Number Mass Number – the mass number of an atom is the ____ of the protons and neutrons in the nucleus of that atom. – Ex: an atom of Al with 13 protons and 14 neutrons has a mass number of 27 Atomic mass is the same as mass number

29 Isotopes Every atom of a given element _____ _____have the same number of neutrons. Isotopes are atoms of the same element that have different numbers of neutrons and different mass numbers Isotopes of an element have the ____ atomic number but different mass numbers because they have different number of neutrons

30 Chapter 4 Section 3 Pg

31 Bohr’s Model of the Atom Bohr was a ______ physicist who worked with Rutherford Bohr _______ with Rutherford’s model, but Bohr’s model focused on the electrons Energy Levels – In Bohr’s model, _________ move with constant speed in fixed orbits around the nucleus (like planets around a sun)

32 Bohr’s Model of the Atom Energy Levels – Each ________ in an atom has a specific amount of energy – If an atom _____ or ______energy, the energy of an electron can change – The possible energies that electrons in an atom can have are called ______ _______ – An electron cannot exist between energy levels

33 Bohr’s Model of the Atom Energy Levels – An electron in an atom can _____ from one energy level to another when the atom gains or loses energy – The _____ of the jump between energy levels determines the amount of energy gained or lost Evidence for Energy Levels – Scientists can measure the energy _______ or released when an electron absorbs or releases energy and moves to higher or lower energy levels

34 Bohr’s Model of the Atom

35 Electron Cloud Model An electron cloud is a ______ model of the most likely locations for electrons in an atom The cloud is _______ at those locations where the probability of finding an electron is high Scientists use the electron cloud model to describe the possible _______ of electrons around the nucleus

36 Atomic Orbitals The ______ _____ represents all the orbitals in an atom An orbital is a region of space around the nucleus where an ______ is likely to be found An electron cloud is a good approximation of how electrons behave in their orbitals

37 Atomic Orbitals Level which an electron has the ____ energy– the lowest energy level– has only one orbital Higher energy levels have _____ than one orbital Each orbital can contain _____ electrons at most

38

39 Electron Configurations An electron configuration is the __________ of electrons in the orbitals of an atom The most ______ electron configuration is the one in which the electrons are in orbitals with the _______ possible energies When all the electrons in an atom have the _______ possible energies, the atom is said to be in its ground state

40 Electron Configurations If a lithium atom ______ enough energy, one of its electrons can move to an orbital with a higher energy, this ____________ is referred to as an excited state An excited state is _____ stable than the ground state Eventually the electron _____ _______and the atom returns to the ground state

41 Electron Configuration Helium, neon, argon, krypton, and xenon atoms _________ from excited states to the ______ state emit the light you see in “neon” lights


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