Chapter 4

1. Atomic Structure Chapter 4

2. If you cut a piece of Aluminum foil in half and continue to cut the resulting piece in half, what will happen? Greek Philosophers pondered this _______________________. • ________________- believed all matter consisted of extremely small particles that could not be divided. • He called these particles __________ • ____________ – did not think there was a limit to the number of times matter could be divided. • Most people believed Aristotle until the _____ when scientists had enough ______ to support Democritus 4.1 Studying Atoms Aristotle thought that all substances were built up from only four elements—_______________________ These elements were a combination of four qualities—hot, cold, dry, and wet. Fire was a combination of hot and dry. Water was a combination of cold and wet.

3. DATLON- born in England in 1766. • He noticed no matter how large or small a sample, the _______________of the elements in a compound is always the _______. • Dalton proposed a theory that all matter is made up of ___________ particles called atoms, which ______ be divided. Dalton’s Atomic Theory Magnesium reacts with oxygen to form the compound magnesium oxide. The ratio of magnesium to oxygen, by mass, in magnesium oxide is always about _______

4. All elements are composed of __________. All atoms of the same element have the same _______, and atoms of different elements have different __________. Compounds contain atoms of more than one ____________. In a particular compound, atoms of different elements always combine the _______________. In Dalton’s model, he thought elements were ____________. Each type of atom is represented by a tiny, solid sphere with a different mass.  Eventually, scientists discovered not all of Dalton’s theories were ____________. MAIN POINTS OF DALTON’S ATOMIC THEORY

5. J.J. Thomson- Joseph John Thomson 1856-1940 • Atoms have __________ and ___________ changes. • Objects with like charges ______, or push apart. • Objects with opposite charges _____ or pull together. • Some charged particles can flow from one location to another (_______________________) • Thomson used an electric current to learn more about _______. Thomson’s model of the atom If amber is rubbed with wool, it becomes charged and can ________ a feather.

6. A cathode-ray tube is a sealed tube with a _____ _____ at each end. One is positive and one is negative. A ______________appears between the two disks. CATHODE-RAY TUBE EXPERIMENT Thomson used a sealed tube of gas in his experiments. When the current was on, the disks became charged and a glowing beam appeared in the tube

7. Thomson discovered the beam was __________ when additional ________ plates were placed on the sides of the tube. Thomson concluded the beam must be _______ charges. He hypothesized the charges came from _____ the atom. Thomson’s experiments provided the first evidence that atoms are made of even _______________________. Cathode ray tube experiment The beam bent _________ a positively charged plate placed outside the tube

8. His model of the atom looked like ______ __________ (or chocolate chip ice cream). The pudding had an overall ________ charge and the __________ charges were randomly placed throughout. Overall, the atom is ___________. Thomson’s model

9. 1899 Ernest Rutherford discovered Uranium emits fast-moving particles that have a _______ charge. (He called them _______ particles) • 1909 he asked his student, Ernest Marsden, to see what happens when the alpha particles are passed through a ______________of gold. • He hypothesized most particles would travel in a _______________ path from their source. • Some would be deflected ______________. Rutherford’s hypothesis

10. Rutherford’s gold foil experiment

11. ACTUAL EXPERIMENTAL RESULTS • More particles were deflected than he was expecting. Some particles deflected as much as _______. Others bounced straight ______. • DISCOVERY OF THE NUCLEUS • Nucleus-______, ________ charged mass located in the ______ of the atom. • Rutherford proposed a new model of the atom. • All of the atom’s positive charge is concentrated in its ________. This explains why alpha particles had a greater _____________ the closer they were to the nucleus (both have ________________charges) Rutherford’s atomic theory If the stadium were a model for an atom, a marble could represent its _________

12. Properties of Subatomic Particles • Protons, electrons, and neutrons are all __________ particles • __________- Positive charge subatomic particle found in the nucleus. They each have a charge of _____. Each nucleus contains at least one particle with a positive charge. • __________- Negatively charged subatomic particle that is found in the space ________ the nucleus. Each electron has a charge of _____. • __________- Neutral subatomic particle that is found in the nucleus of an atom. It’s mass is nearly equal to the mass of a proton. • In 1932- ________________designed an experiment to show neutrons exist. It was similar to Rutherford’s gold foil experiment. The neutrons showed no deflection. 4.2 structure of an atom

13. Protons, electrons and neutrons can be distinguished by _______, ________, and ________ in the atom. • Protons and neutrons have ______ mass. Electrons are ________ the mass of a proton. • Electrons have a charge that is equal in size to, but the _____________ of, the charge of a proton. Neutrons have ___________________. • Protons and neutrons are found in the _________, but electrons are found in the space ___________ the nucleus. Comparing Subatomic Particles

14. Atomic number- Equal to the number of _________ in an atom of that element. • Hydrogen (H) atoms are the only atoms with __ proton. • Atoms of different elements have _______________ of protons. • Each positive charge is _________ by a negative charge. Atomic Number and mass number Each element has a different atomic number. A The atomic number of sulfur (S) is ___. B The atomic number of iron (Fe) is ___. C The atomic number of silver (Ag) is ___.

15. Mass number- Sum of the ________ and ___________ in the nucleus of that atom. • # of neutrons = • Isotopes • Every atom of a given element ______have the same number of protons and electrons. • But every atom of a given element _______have the same number of neutrons. • Isotopes of an element have the same ________ _______ but a different mass number because they have different numbers of _____________.

16. With most elements, it’s hard to notice any differences in the physical or chemical properties of their__________. Hydrogen is the ____________. Normal hydrogen (H-1) has ____________(most of all H) H-2 has 1 neutron –mass has doubled. H-3 has 2 neutrons –mass has tripled. ______________is made from H-2 atoms.

17. BOHR’S MODEL OF THE ATOM • Niels Bohr’s model did something Rutherford’s model did not do. It focused on the __________. • Electrons move with constant _______ in _____ orbits around the nucleus (like planets around the sun) • Each electron in an atom has a specific amount of __________. • _______________-the possible energies that electrons in an atom can have. 4.3 modern atomic theory

18. Picture energy levels as steps in a ______________. • You can go up or down the steps, but only in whole-step increments. You cannot stand _________________on a staircase. Electrons cannot ______ between energy levels. • An electron in an atom can move from one energy level to another when the atom gains or loses ______. • The size of the jump determines the amount of energy __________________________. • Energy is __________ as the electron jumps back down to its ________ energy levels is often given off in the form of _________________. • Different elements emit different ____________ of light. Understanding energy levels

19. Bohr was incorrect in assuming electrons moved like planets in a _______________. They are actually less _________________. ___________________-a visual model of the most likely locations for electrons in an atom. The cloud is _________ at the locations where the probability of finding an electron is _______. Scientists use the electron cloud model to describe the ________ locations of electrons around the _____________. ELECTRON CLOUD MODEL

20. Electro n cloud analogy When the propeller of an airplane is at rest, you can see the___________ofthe blades. When the propeller is moving, you see only a ____ that is similar to a drawing of an electron cloud

21. Orbital- is a region of space around the nucleus where an electron is _________ to be found. An electron cloud is a good _______________ of how electrons behave in their ____________ The level in which an electron has the __________—the lowest energy level—has only _____ orbital. Higher energy levels have _________________orbital Atomic orbitals

22. electron configuration is the arrangement of electrons in the ___________ 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 lowest possible energies, the atom is said to be in its ______________ • If one electron can move to an orbital with a higher _________ it is referred to as an ______________. • An excited state is _________than the ground state. Electron configurations