Ch. 5: Atomic Structure Standards: Matter consists of atoms that have internal structures that dictate their chemical and physical behavior. Targets: State the position of protons, neutrons and electrons in the atom State the relative masses and relative charges of protons, neutrons and electrons. Define the terms mass number (A), atomic number (Z) and isotopes of an element. Deduce the symbol for an isotope given its mass number and atomic number. Calculate the number of protons, neutrons and electrons in atoms and ions from the mass number, atomic number and charge. Calculate the relative atomic mass given the abundance and isotopes of an element State how the periodic table is organized by atomic number, groups, and periods.

State the position of protons, neutrons and electrons in the atom History of Atomic Theory Democritus (420 BCE) Greek philosopher; matter composed of small particles-atoms: purely hypothesis, no data Aristotle ( BCE) Greek philosopher; matter composed of earth, air, fire, water. This view dominated thought until 17th century John Dalton ( ) English chemist; was the first to base atomic theory on scientific evidence.

State the position of protons, neutrons and electrons in the atom Dalton’s Atomic Theory Elements are made of tiny particles called atoms. All atoms of a given element are identical. The atoms of a given element are different from those of any other element. Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative number of types of atoms. Atoms cannot be created, nor divided into smaller particles, nor destroyed in the chemical process. A chemical reaction simply changes the way atoms are grouped together.

State the position of protons, neutrons and electrons in the atom Evidence for sub-atomic particles 1897: J.J. Thomsen: Cathode Ray Tube Evidence for electrons: Bent a stream of rays originating from the negative electrode (cathode). Stream of particles with mass & negative charge. 1909: Ernest Rutherford: Gold Foil Evidence for protons & nucleus: Alpha particles deflected passing through gold foil 1932: James Chadwick: Beryllium Evidence for neutrons: Alpha particles caused beryllium to emit rays that could pass through lead but not be deflected,

State the position of protons, neutrons and electrons in the atom. State the relative masses and relative charges of protons, neutrons and electrons. Atomic Structure –Nucleus: center –Electron Cloud: outside (Draw and label a diagram of an atom) Atomic Particles *In a neutral atom: # of protons = # of electrons ParticleLocationChargeRelative Mass Proton (p + )Nucleus+ (positive) 1 amu Neutron (n o )Nucleus0 (no charge)1 amu Electron (e - )Cloud- (negative) 0 amu

Atomic Number (Z) The atomic number is the number of protons in the nucleus. It determines the identity of an atom. All oxygen atoms have 8 protons in the nucleus All lead atoms have 82 protons in the nucleus Define the terms mass number (A), atomic number (Z), and isotope of an element

Atomic Number (Z) It also tells us the number of electrons in a neutral atom A neutral sodium atom contains 11 protons and 11 electrons A neutral bromine atom contains 35 protons and 35 electrons Define the terms mass number (A), atomic number (Z), and isotope of an element

8 Find the Atomic Number (Z) for the following: –Nitrogen –Potassium –Iodine –How many protons do the above atoms have? –How many electrons do the above atoms have?

9 Define the terms mass number (A), atomic number (Z), and isotope of an element Find the Atomic Number (Z) for the following: –Nitrogen: 7 –Potassium: 19 –Iodine: 53 –How many protons do the above atoms have? –How many electrons do the above atoms have? –N: 7, K: 19, I: 53

Mass Number (A) It is not practical to measure the masses of atoms in grams due to their small size. Scientists devised a measurement called atomic mass units (amu). Protons have a mass of 1 amu Neutrons have mass of 1 amu Electrons have mass of 0 amu. Define the terms mass number (A), atomic number (Z), and isotope of an element

Mass Number (A) Mass number = # protons + # neutrons To find neutrons, subtract the atomic number from the mass number Ex: Sodium Z: 11, A: 23, how many neutrons? = 12 neutrons Define the terms mass number (A), atomic number (Z), and isotope of an element

12 Define the terms mass number (A), atomic number (Z), and isotope of an element Find the mass number (A) for the following elements: –Oxygen –Sodium –Arsenic –How many protons do these atoms have? –How many neutrons do these atoms have?

13 Define the terms mass number (A), atomic number (Z), and isotope of an element Find the mass number (A) for the following elements: –Oxygen: 16 –Potassium: –Arsenic: –How many protons do these atoms have? –O:8, K:19, As:33 –How many neutrons do these atoms have? –O: 8, K:, As:

Isotope Atoms of the same element can have different numbers of neutrons, thus they will have different masses. These are called isotopes of the element. Define the terms mass number (A), atomic number (Z), and isotope of an element

Isotope There are three isotopes of hydrogen: Hydrogen-1 has 1 proton, 1 electron, 0 neutrons Hydrogen-2 has 1 proton, 1 electron, 1 neutron Hydrogen-3 has 1 proton, 1 electron, 2 neutrons Define the terms mass number (A), atomic number (Z), and isotope of an element

Names for Isotopes: Name of element – Mass Number Symbols for Isotopes: Deduce the symbol for an isotope given its mass number and atomic number Element Symbol Mass Number Atomic Number

Deduce the symbol for an isotope given its mass number and atomic number Consider an atom that has an atomic number (Z) of 29 and a mass number (A) of 63. What is its name and symbol? atomic number of 29 identifies it as copper Name: Symbol:

Deduce the symbol for an isotope given its mass number and atomic number Consider an atom that has an atomic number (Z) of 29 and a mass number (A) of 63. What is its name and symbol? atomic number of 29 identifies it as copper Name: Copper-63 Symbol: 63 Cu 29

Deduce the symbol for an isotope given its mass number and atomic number Consider an atom that has an atomic number Consider an atom that has A=32 and Z=16. What is its name and symbol? Z=16 identifies it as sulfur Name: Symbol:

Deduce the symbol for an isotope given its mass number and atomic number Consider an atom that has A=32 and Z=16. What is its name and symbol? Z=16 identifies it as sulfur Name: Sulfur-32 Symbol: 32 S 16

Consider an atom that has an atomic number of 74 and a mass number of 185. What is its name and symbol? Deduce the symbol for an isotope given its mass number and atomic number

Consider an atom that has an atomic number of 74 and a mass number of 185. What is its name and symbol? atomic number of 74 identifies it as tungsten Name: Tungsten-185 Symbol: 185 W 74

Consider an atom that has A=127 and Z=53. What is its name and symbol? Deduce the symbol for an isotope given its mass number and atomic number

CConsider an atom that has A=127 and Z=53. What is its name and symbol? Z=53 identifies it as iodine Name: Iodine-127 Symbol: 127 I 53

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge Consider the neutral carbon-12 atom. How many protons, neutrons, and electrons are in an atom and what is the name and symbol? Atomic mass = Atomic number = Protons = Neutrons = Electrons = Name is Symbol is

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge Consider the neutral carbon-12 atom. How many protons, neutrons, and electrons are in an atom and what is the name and symbol? Atomic mass = 12 Atomic number = 6 Protons = 6 (atomic number) Neutrons = 6 (mass – protons) Electrons = 6 (neutral atom so same as protons) Name is Carbon-12 Symbol is 12 C 6

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge Consider an atom that has 9 protons, 9 electrons, and 10 neutrons. What is its atomic number, atomic mass, name, and symbol? Z= A= Name: Symbol:

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge Consider an atom that has 9 protons, 9 electrons, and 10 neutrons. What is its atomic number, atomic mass, name, and symbol? Z=9 (atomic number = # protons) A=19 (atomic mass = protons + neutrons) Fluorine-19 (name and mass) 19 F (neutral because protons = electrons) 9

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge Consider a neutral atom with A=75 and Z=33. How many protons, neutrons, and electrons are in the atom. What is the name and symbol? Consider a neutral atom with A=77 and Z=33. How many protons, neutrons, and electrons are in the atom. What is the name and symbol?

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge Consider a neutral atom with A=75 and Z=33. How many protons, neutrons, and electrons are in the atom. What is the name and symbol? Protons = 33Neutrons = 42Electrons = 33 Name: Arsenic-75 Symbol: 75 As 33 Consider a neutral atom with A=77 and Z=33. How many protons, neutrons, and electrons are in the atom. What is the name and symbol? Protons = 33Neutrons = 44Electrons = 33 Name: Arsenic-77 Symbol: 77 As 33 pg 116: Practice problems 9,10,11 pg 117: Practice problems 12,13

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge Ions are charged particles formed when atoms gain or lose electrons resulting in unequal numbers of protons and electrons Cations: Atoms that lose electrons become positively charged Anions: Atoms that gain electrons become negatively charged

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge How many protons, neutrons, and electrons are in an ion of K-39 that has lost one electron? What is the charge of the ion? What is its symbol?

Calculate the number of protons, neutrons, and electrons in atoms and ions from the mass number, atomic number, and charge How many protons, neutrons, and electrons are in an ion of K-39 that has lost one electron? What is the charge of the ion? What is its symbol? Name: Potassium-39 Protons = 19 Neutrons = 20 Electrons = 18 Charge = 1+ or +1Symbol is 39 K 1+ 19

34 Create an Atom Choose any element with atomic number 20 or above. Write the: 1) Element name 2) Chemical symbol (not JUST the 1-2 letter combo) 3) Atomic number (Z) 4) Atomic mass (A) 5) Number of protons 6) Number of neutrons (show how you determine this) 7) Number of electrons 8) Now draw AND LABEL your atom with the proper number of protons, neutrons and electrons, making sure that the particles are placed in the proper locations.

35 Create an Isotope For the neutral atom you already drew, determine it’s new atomic mass (add or subtract no more than 3). Write the: 1) Isotope name (which should indicate the mass) 2) isotope symbol 3) Number of protons 4) Number of neutrons (show how you determine this) 5) Number of electrons 6) Now draw the isotope version of your atom.

36 Create an Ion Using your neutral atom, If a metal, subtract electrons, if a nonmetal add electrons. Write the: 1) Isotope name (which should indicate the mass) 2) Isotope symbol 3) Number of protons 4) Number of neutrons (show how you determine this) 5) Number of electrons 6) Now draw the ions version of your atom.

Calculate the relative atomic mass of an element In nature, most elements occur as a mixture of two or more isotopes. The average atomic mass is calculated using the percent abundance and mass of each isotope..

Calculate the relative atomic mass of an element The average atomic mass of chlorine is , the two isotopes are Cl-35 and Cl-37. Which isotope is more abundant? Cl-35 is closer to , therefore it is more abundant.

Calculate the relative atomic mass of an element Three things are needed to determine the average atomic mass (aka relative atomic mass) Number of stable isotopes of the elements Mass of each isotope Percent abundance of each isotope

Calculate the relative atomic mass of an element Steps to Calculate Average Atomic Mass: 1.Convert % to decimal  move decimal 2 places to left 2.Multiply abundance by mass for each isotope 3.Add products together

Calculate the relative atomic mass of an element Calculate the average atomic mass of Chlorine. Cl-35 has a mass of and a relative abundance of 75.7%; Cl-37 has a mass of and a relative abundance of 24.3% .757; 24.3  (.757)=26.472; (.243)= =

Calculate the relative atomic mass of an element Calculate the average atomic mass of Oxygen. O-16 has a mass of and a relative abundance of 99.76%; O-17 has a mass of and a relative abundance of 0.037%; O-18 has a mass of and a relative abundance of 0.204% .9976;  ;  (.9976)=15.957; ( )= ; ( ) = = (GO TO PRACTICE PROBLEMS)

Revisit Slide 31 White board practice writing ions in name and in symbol, ex. Calcium – or 41 Ca

44 State how the modern periodic table is organized by atomic number, groups, and periods. Periodic Table Organization Elements are listed in order of increasing atomic number from left to right and top to bottom Rows are called periods – there are 7 periods 44

45 State how the modern periodic table is organized by atomic number, groups, and periods. Columns are called groups or families – elements in groups have similar physical and chemcial properties 45

46 State how the modern periodic table is organized by atomic number, groups, and periods. Classes of Elements – Metals high conductivity, high luster (when clean), ductile, malleable located on the left side and the center of the periodic table (excluding Hydrogen) 46

47 State how the modern periodic table is organized by atomic number, groups, and periods. Classes of Elements – Nonmetals nonlustrous, poor conductors, can be a gas, liquid or solid located on the right side 47

48 State how the modern periodic table is organized by atomic number, groups, and periods. Classes of Elements – Metalloids properties are intermediate between metals and nonmetals Located along stair-step line 48