JOURNAL 10/26 Which has the largest atomic number? K, Na, or P Which has the largest atomic radius?- Ca, Sr, Ba

The Periodic Table and Periodicity

A. Dmitri Mendeleev  Dmitri Mendeleev (1869, Russian) Organized elements by increasing atomic mass. Predicted the existence of undiscovered elements.

B. Henry Mosely  Henry Mosely (1913, British) Organized elements by increasing atomic number. Fixed problems in Mendeleev’s arrangement.

 Periodic Law Properties of elements repeat periodically when the elements are arranged by increasing atomic number. A. Terms

Arrangement In order of increasing atomic number in specific columns and rows.

Groups- vertical columns of the PT The Periodic Table

Periods- horizontal row on the PT The Periodic Table

Groups are important on the PT Why?  The elements in a group have similar chemical and physical properties!

Alkali Metals – Group H 2 Li 3 Na 4 K 5 Rb 6 Cs 7 Fr

Alkaline Earth Metals – Group Be 3 Mg 4 Ca 5 Sr 6 Ba 7 Ra

Halogens – Group F 3 Cl 4 Br 5 I 6 At 7

Noble Gases – Group He 2 Ne 3 Ar 4 Kr 5 Xe 6 Rn 7

Transition Metals – Groups

Inner Transition Metals La Yb Ac No

Metals on the PT

Metals Metals are lustrous (shiny), malleable, ductile, and are good conductors of heat and electricity. They are mostly solids at room temp. What is one exception?

Nonmetals - Lack properties of metals

Nonmetals Nonmetals are the opposite. They are dull, brittle, nonconductors (insulators). Some are solid, but many are gases, and Bromine is a liquid.

Metalloids (semi-metals)- have a mixture of metallic and nonmetallic properties Si 4 GeAs 5 SbTe 6 PoAt 7

Metalloids Metalloids, aka semi-metals are just that. They have characteristics of both metals and nonmetals. They are shiny but brittle. And they are semiconductors. What is our most important semiconductor?

INCREASES INCREASES BOILING POINT & MELTING POINT VS. ATOMIC NUMBER

Diatomic Elements Most elements can be isolated to atomic elements – individual atoms 7 elements are too reactive to exist as individual atoms, instead, they are found as molecular elements – 2 atoms bonded together Hydrogen, H 2 Oxygen, O 2 Nitrogen, N 2 Chlorine, Cl 2 Bromine, Br 2 Iodine, I 2 Fluorine, F 2

Trends Atomic radii & Ionic radii  Increase down a group Why? greater shielding  Decrease across a period Why? Greater effective nuclear charge

Atomic Radii one-half the distance between the nuclei of identical atoms that are bonded together.

#1. Atomic Size - Group trends u As we increase the atomic number (or go down a group)... u each atom has another energy level, u so the atoms get bigger. H Li Na K Rb

#1. Atomic Size - Period Trends u Going from left to right across a period, the size gets smaller. u Electrons are in the same energy level. u But, there is more nuclear charge. u Outermost electrons are pulled closer. NaMgAlSiPSClAr

Atomic Size Decreases left to right u Why? As you move across a period, the atom gains electrons as well as protons. Because the u effective nuclear charge has increased, the electrons will therefore be pulled closer to the u nucleus, causing the atom to become smaller.

Atomic Size (radius) Size tends to increase down a column. Size tends to decrease across a row.

B. Periodic Trends  Atomic Radius Increases to the LEFT and DOWN.

Atomic Number Atomic Radius (pm) H Li Ne Ar 10 Na K Kr Rb 3 Period 2

Ionic Radii – the size of an ion. Cation – a positive ion:Na+,Mg2+,Fe2+, Fe3+, – Formed by the loss of an electron – Cations are smaller than their neutral atom. As an electron is lost, the effective nuclear charge is greater, causing the electron cloud to become pulled closer to the nucleus, making it smaller

Anion – a negative ion: Cl-, F-, N3-, … – Formed by the gain of an electron(s). – As an electron is added, the nucleus remains the same so the electrons are not drawn as close to the nucleus. Also, added electron causes repulsion among other electrons.

Ion Group trends u Each step down a group is adding an energy level u Ions therefore get bigger as you go down, because of the additional energy level. Li 1+ Na 1+ K 1+ Rb 1+ Cs 1+

Ion Period Trends u Across the period from left to right, the nuclear charge increases - so they get smaller. u Notice the energy level changes between anions and cations. Li 1+ Be 2+ B 3+ C 4+ N 3- O 2- F 1-

Atomic size and Ionic size increase in these directions:

Trends Ionization energy & Electronegativity  Decrease down a group Why? Greater shielding  Increase across a period Why? Greater effective nuclear charge

Ionization Energy Energy required to remove one electron from an atom Ion – an atom or group of bonded atoms that has a positive or negative charge. – Ex. Na +, Cl -, O 2-, Fe 3+, NH 4 +, CO 3 2-, … – Monatomic ion – ion containing one atom – Polyatomic ion – ion containing atoms bonded together

Ionization Energy

Noble Gases have the highest ionization energies because they have a full octet Group IA have the lowest ionization Energies Decreases down a group because electrons in higher energy levels are easier to remove Increases across period because more electrons in an energy level make it more difficult to get to the magic number of 8

Electronegativity a measure of the ability of an atom in a chemical compound to attract electrons – In a chemical compound, the more electronegative atom will attract electrons more – Ex. HCl : H-Cl : electrons are pulled closer to Cl

The most electronegative atom on the Periodic Table is Fluorine Electronegativity tends to increase across a period Electronegativity tends to decrease down agroup