2 AtomsThe atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons
18 Atomic NumberAtomic number of an element equals the number of protons in an atom of that element
19 The atomic number also equals the amount of electrons and atom has Atoms are neutral because they have the same number of electrons and protonsTherefore…The atomic number also equals the amount of electrons and atom has
20 Atomic number gives the number of protons, nut not the # of neutrons Mass NumberAtomic number gives the number of protons, nut not the # of neutronsMass number is the sum of the protons and neutrons
21 Atom of aluminum has 13 protons and 14 neutrons, what is its mass number?
22 Dalton thought that all atoms of a given element were identical IsotopesDalton thought that all atoms of a given element were identicalEvery atom of a given element does have the same amount of protons and electrons,
23 IsotopesBut every atom of a given element does not have the same number of neutronsIsotopes are atoms of the same element that have different numbers of neutrons and different mass numbers
24 What are some effects of water water that contains hydrogen isotopes? Look at figure 12 on page 112What are some effects of water water that contains hydrogen isotopes?
25 With a group of 2-31. How are the compositions of heavy water and ordinary water similar?What type of hydrogen atoms does ordinary water contain?What type of hydrogen atoms does heavy water contain?Compare the properties of heavy water and ordinary water.
26 Complete section one and 2 in your workbook When complete…Complete section one and 2 in your workbookWhat you do not finish in class will be homework
27 BellworkHow many neutrons are in an atom with an atomic number of 32 and an atomic mass of 68?
28 Atom http://www.youtube.com/watch?v=yqLlgIaz1L0
29 BohrBohr’s model of the atom focused on the electron which is what makes his model the modern model
30 Energy LevelsElectrons move with constant speed in fixed orbits around the nucleusEach electron has a specific amount of energySometimes atoms gain or lose energy and the energy in an electron can change
31 Energy LevelsEnergy levels: The possible energies that an electron can have.The electrons in an atom can move from one energy level to another when they gain or lose energy
33 How do we know?Scientists can measure the energy gained when electrons absorb energy and move to a higher energy levelThey can also measure the energy released when an electron moves to a lower energy level
34 How do we know?Some elements emit light when they release energyExplosions can cause heat which pushes electrons to higher energy levels
35 Electron cloudThe electron cloud model is used to describe the possible locations of electrons around the nucleus.
36 Atomic OrbitalsOrbital is the region of space around the nucleus where the electron is likely to be