Matter and Environment: ENVIRONMENT PERIODIC TRENDS PERIODIC TRENDS INDICATORS A periodic trend is an indicator of how elements’ properties change as you move across the periodic table. ELEMENT PROPERTIES FOUR DIFFERENT We will study four different properties and their organization within the periodic table: 1. Atomic size 2. Ionization energy 3. Electronegativity 4. Reactivity ATOMIC SIZE (aka ATOMIC RADIUS) ATOMIC SIZE RADIUS Atomic size refers to the distance from an atom’s nucleus to its valence shell. (the highest energy level) 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 ATOMIC SIZE RADIUS Atomic size increases as you move down a group because there are more energy levels 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 ATOMIC SIZE RADIUS Atomic size increases as you move left on the periodic table because there are fewer protons pulling on the electrons. *SHIELDING EFFECT - the more energy levels you have, the less protons “pull” on electrons 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 ATOMIC SIZE RADIUS So basically… atomic size increases as you move down and as you move left. ATOMIC SIZE RADIUS IONIZATION ENERGY ION REMOVAL Ionization energy is the energy necessary to remove an electron from a neutral atom, starting from the last energy level (valence shell). LOW IONIZATION ENERGY = it is easy to remove electrons = elements are MORE LIKELY TO BECOME CATIONS HIGH IONIZATION ENERGY = it is difficult to remove electrons = elements are MORE LIKELY TO BECOME ANIONS. 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 IONIZATION ENERGY ION REMOVAL Ionization energy increases as you move up a group because there are less energy levels “shielding” the electrons from the protons’ “pull” 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 IONIZATION ENERGY ION REMOVAL Ionization energy increases as you move left across a period because there are more protons and so the positive charge increases. 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 IONIZATION ENERGY ION REMOVAL So basically… ionization energy increases as you move up and as you move right. ⏬ ⏫ IONIZATION ENERGY ION REMOVAL ELECTRONEGATIVITY ATTRACTION Electronegativity is a measure of how easy it is to attract and retain electrons in an atom when it forms a chemical bond. LOW ELECTRONEGATIVITY = it is difficult for an element to attract electrons (easy to let them go); elements are MORE LIKELY TO BECOME CATIONS HIGH ELECTRONEGATIVITY = it is easy for an element to attract electrons; elements are MORE LIKELY TO BECOME ANIONS. Ca+ion Anion- 💧 ( 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 ⤫ ELECTRONEGATIVITY ATTRACTION ⤫ ⤫ ⤫ ⤫ ⤫ ⤫ Noble Gases are stable or “inert” so they do not attract electrons, thus Electronegativity equals zero (0) Electronegativity increases as you move up a group because there are less energy levels “shielding” the electrons from the protons’ “pull” ELECTRONEGATIVITY ATTRACTION 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 ⤫ ⤫ ⤫ ⤫ ⤫ ⤫ ⤫ Noble Gases are stable or “inert” so they do not attract electrons, thus Electronegativity equals zero (0) Electronegativity increases as you move right across a period because elements have more electrons, (i.e. elements’ valence shells are more than half full, so it is easier to attract electrons than to lose them). ELECTRONEGATIVITY ATTRACTION 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 🔻 ⤫ ⤫ ⤫ ⤫ ⤫ ⤫ ⤫ Noble Gases are stable or “inert” so they do not attract electrons, thus Electronegativity equals zero (0) So basically… electronegativity increases as you move up and as you move right. ⏬ ⏫ REACTIVITY ATTRACTION Elements that are reactive are those that easily form bonds with other elements to form compounds. Having an incomplete valence shell, (i.e. electrons still ‘fit’ into the last energy level). REACTIVITY IN METALS ATTRACTION Metals react more easily the farther left and farther down they are in the periodic table. FARTHER LEFT = fewer electrons FARTHER DOWN = more energy levels = farther away from nucleus = weaker “pull” from protons REACTIVITY IN METALS ATTRACTION 1 1 18 2 M E TA L S 2 3 4 5 6 7 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 REACTIVITY IN NON-METALS ATTRACTION Nonmetals react more easily the farther right and farther up they are in the periodic table. FARTHER RIGHT = more electrons = fewer “spots to fill” FARTHER UP = fewer energy levels = closer to nucleus = stronger “pull” from protons REACTIVITY IN METALS ATTRACTION 1 1 18 2 13 14 15 16 17 N O N - M E TA L S 2 3 4 5 6 7 3 4 5 6 7 8 9 10 11 12 Metal Reactivity Increases REACTIVITY ATTRACTION ⤫ F ⤫ ⤫ ⤫ ⤫ ⤫ Fr ⤫ Non-Metal Reactivity Increases TO RECAP SO, BASICALLY… THIS % egativity egativity 🌟 🔵 ONE LAST THING THE OCTET (8) RULE THE PERFECT BALANCE All atoms (except Hydrogen) want to have 8 electrons in their outermost energy level (valence shell) Noble gases have 8 electrons in their valence shell. This is why they are so stable and unreactive. Atoms with few (<4) valence electrons will lose them when forming bonds. Atoms with many (>5) valence electrons will gain electrons THE OCTET (8) RULE IN ACTION Atoms with few (<4) valence electrons will lose them when forming bonds. Atoms with many (>5) valence electrons will gain electrons Example: NaCl END OF PRESENTATION
