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The Octet Game -Create an individualized Symbol -Draw that Symbol anywhere between 1-7 times on you sticky note -LETS PLAY TRENDS OF THE PERIODIC TABLE Atomic Radius Ionization Energy Electronegativity VOCAB: ATOMIC RADIUS Atomic Radius of an element is defined as half the distance between two bonded atoms of the same element. A more simple (but not technically correct) definition is the distance from the center of the atom to the outermost electrons VOCAB: IONIZATION ENERGY An atom’s ionization energy (IE) is the amount of energy necessary to remove one of its electrons (make an ion) Think of the ionization energy as strongly an atom holds onto its outermost electrons The higher the ionization energy, the harder it is to remove an electron VOCAB: ELECTRONEGATIVITY Electronegativity shows an atom’s ability to attract electrons i.e. How badly does the atom want to gain electrons - Electronegativity is expressed as just a number (like “on a scale of 0-4”) TRENDS OF THE PERIODIC TABLE Atomic Radius Ionization Energy Electronegativity VOCAB: VALANCE ELECTRONS Valance electrons are the electrons in the last shell or energy level of an atom The number of valance electrons determines the atom’s properties/reactivity How many valance electrons does Ge have? Cl? Ba? PERIODIC TREND 1: ATOMIC RADIUS Radius is the distance from the center of the atom to the outermost electrons Remember… The majority of the atom is empty space, with the electrons orbiting the nucleus PERIODIC TREND 1: ATOMIC RADIUS So… As you move down a group (column), atomic radius increases This should make sense because as you go down a group, the number increases as does the number of electrons NOTE, THAT AS YOU MOVE ACROSS A PERIOD (FROM LEFT TO RIGHT) ATOMIC RADIUS DECREASES! WHY? As you move across a period, the outer electrons are all in the same what? What increases as you move across a period? Protons and electrons have what kind of charges? Positive and negative charges do what? PERIODIC TREND 1: ATOMIC RADIUS So… Because the number of protons increases across a period, the larger + charge in the nucleus pulls the electrons further in, reducing atomic radius As you move across a period (left to right) atomic radius decreases SUMMARY: As you move down a group (column), atomic radius increases As you move across a period (left to right) atomic radius decreases ION REVIEW… Ions are atoms that have a + or – charge because they lost or gained electrons Positive ions (cations) have LOST e- and negitave ions (anions) have GAINED e- The Noble Gases (group 18) are very stable elements WHY DO ELEMENTS FORM IONS? Remember that atoms like to be stable (i.e. stable e- configurations) like the noble gases Groups 1 & 2 will lose a number of e- (form cations) to get to a noble gas config Groups 15, 16, & 17 will gain a number of e(form anions) to get to a noble gas The other groups vary, and we will ignore them for now PERIODIC TREND 2: IONS AND IONIC SIZE Groups 1 & 2 When these elements lose e- to form cations, they eliminate a quantum level (shell) and create more of a pull towards the + nucleus. So positive ions (cations) become smaller than their neutral forms Group 1 atom and ion size PERIODIC TREND 2: IONS AND IONIC SIZE Groups 15,16, and 17 When these elements gain e- to form anions, the negative charges of the electrons repel each other, which increases the size of the overall ion. Negative ions (anions) are larger than their neutral atom counterparts Group 17 atom and ion size TRENDS OF THE PERIODIC TABLE Atomic Radius Ionization Energy Electronegativity PRACTICE 1. Which has the larger atomic radius: a) Br or I? d) Zn or Fe? b) Ar or K? e) N or N-3 ? c) Li or Li+ ? 2. Write the symbol for the ions that form from: a) Rubidium c) Phosphorous b) Fluorine d) Beryllium PERIODIC TREND 3: IONIZATION ENERGY An atom’s ionization energy (IE) is the amount of energy necessary to remove one of its electrons (make an ion) The higher the ionization energy, the harder it is to remove an electron Which elements do you think will have high IE? PERIODIC TREND 3: IONIZATION ENERGY What was, and how did we explain, the atomic radius trend? Ionization energies decrease as you move down a group. Ionization energies increase as you move from left to right across a period. Does this sound familiar? PERIODIC TREND 4: ELECTRONEGATIVITY Electronegativity shows an atom’s ability to attract electrons i.e. How badly does the atom want to gain electrons - Electronegativity is expressed as just a number (like “on a scale of 0-4”) • Fluorine the most electronegative element, while Francium is the least. PERIODIC TREND 4: ELECTRONEGATIVITY Electronegativity values increase as we go from left to right across a period Electronegativity values decrease as you move down a group The cause of these patterns has to do with something called electron affinity which we will not discuss because if we did, your heads might explode. So lets just describe the trend and leave it at that, ok?