Dmitri Mendeleev The Periodic Table of the Elements

Dmitri Mendeleev and the 1st Periodic Table Photo by Jurii A Russian chemist named Dmitri Mendeleev created the first widely accepted periodic table. He still relied on this idea of 8 groups, but he understood that many elements were still missing. He placed gaps in his periodic table where he thought these elements belonged, and he correctly predicted these elements properties which validated his ordering of the elements.

Elements are arranged and identified on the periodic table by the number of protons they have in their nucleus. The atomic number is equal to the number of protons in an element. In its uncharged atomic state, it is also equal to the number of electrons.

Approximately 1 mole of Si Elements also has an atomic mass listed. Remember atomic mass of an element is different than the mass number of an isotope. 28.1 grams of silicon Approximately 1 mole of Si The atomic mass is equal to the number of grams in 1 mole of an element. Atomic mass is sometimes referred to as atomic weight.

It is very important that you can use the periodic table to distinguish metals from nonmetals. Find the dark jagged line on the Periodic Table On the left side of this line are all of the metals On the right side of this line are all of the nonmetals

Metals donate or lose electrons when they become ions. + 2 Metals donate or lose electrons when they become ions. Beryllium This gives metals a positive charge. Positively charged ions are called cations. + 1 When elements lose electrons and increase their charge, we say that they have been oxidized. Sodium

Nonmetals gain or accept electrons when they become ions. - 2 Nonmetals gain or accept electrons when they become ions. This gives nonmetals a negative charge. Negatively charged ions are called anions. Oxygen - 1 When elements gain electrons and lower their charge, we say that they have been reduced. Chlorine

metals react with nonmetals! Metals lose/donate electrons and nonmetals gain/accept electrons This is why metals react with nonmetals! +1 -1 sodium sodium chloride chlorine

Think about counting from the outside to the inside! You need to understand the pattern of elements gaining and donating electrons on the periodic table. Does NOT gain or lose donate 1 electron gains 2 electrons gains 1 electrons donate 2 electron Think about counting from the outside to the inside!

The metals in the middle of the periodic table are known as the transition metals.

The elements that lay on either side of the dark, jagged have rather unique properties. Sometimes they behave like metals, and sometimes they behave like nonmetals. Because of this, they are called Metalloids

You also need to know that Iron, Cobalt, and Nickel have special properties such as the ability to be made into magnets. Together, these three elements are known as the . Iron Triad Iron Triad

The elements whose valence electrons are in the s and p sublevels are known as the representative elements. The number of valence electrons of these elements is followed by an A. s p

The elements whose valence electrons are in the d and f sublevels are known as the transition elements. The number of valence electrons of these elements is followed by a B. d f

There are several groups/families on the periodic table whose name you should have memorized. Group 1 = Alkali Metals Group 2 = Alkaline Earth Metals Group 17 = Halogens Group 18 = Noble Gases Noble Gases Alkali Metals Halogens Alkaline Earth Metals

Columns on the periodic table are known as groups or families. All of the elements in group 16 have 6 valence electrons Elements in the same group/family have similar physical and chemical properties because they all have the same number of valence electrons!

How many valence electrons do the elements of group 2 have? 6B = 6

How many valence electrons do the elements of group 17 have? How many valence electrons does sulfur have? 7A = 7 6A = 6

Inert means they resist chemical reactions! Which group on the periodic table undergoes the fewest chemical reactions? Group 18 The Noble Gases They are inert gases. This is because they have 8 valence electrons and their s and p sublevels are full. Inert means they resist chemical reactions!

The Periodic Table can be used to determine the charge of the representative elements when they become ions! +1 +4 or -4 +2 +3 -3 -2 -1 20

Determine the charge of each of the elements on your notes. +1 -1 +2 -2 -3 -1 -2 +1 +2 +2 -1 Noble Gases do not become ions. This is why we say they have a charge of zero (0)

Iron (III) has a ____ charge. +3 Iron (II) has a ____ charge. +2 The transition metals are the d-block elements. Because of this, the number of electrons they will lose is less predictable. You will know the charge of a transition metal by the roman numeral in its name! Iron (III) has a ____ charge. +3 Iron (II) has a ____ charge. +2 copper (I) has a ____ charge. +1 copper (II) has a ____ charge. +2

Determine the charge of each of the transition metals on your notes. +2 +4 +3 +4 +2 +3

+ Why is the charge of a transition metal always positive? Metals Remember: Metals ______________ electrons. This gives them a ____ charge. Positively charged ions are called ________. lose/donate + cations Since all of the transition elements are metals, they will all be cations!

Ionic compounds are ALWAYS between a metal and a nonmetal. On the left side of this line are all of the metals On the right side of this line are all of the nonmetals

Covalent compounds are ALWAYS between nonmetals. Covalent compounds occur because nonmetals can also share electrons with other nonmetals On the right side of this line are all of the nonmetals

Understanding the previous facts at a conceptual level is critical to your success in chemistry. Using this knowledge, determine the identity of each of the following unknown elements. NaX The formula above shows the ratio of an unidentified element, X, to sodium in an ionic salt. In which group on the periodic table does Element X most likely belong? A Group 1 B Group 2 C Group 17 D Group 18 Since it is an ionic salt, it has to be a nonmetal since sodium is a metal. It cannot be group 18 since group 18 is the inert noble gases that would not react with sodium.

XF The formula above shows the ratio of an unidentified element, X, to fluorine in an ionic salt. Which group below is most likely the identity of Element X? A sulfur B lithium C arsenic D krypton Since it is an ionic salt, it has to be a metal since fluorine is a nonmetal. Ionic compounds have both a metal and a nonmetal.

XCl3 The formula above shows the ratio of an unidentified element, X, to chlorine in a covalent molecule. Which element below is most likely the identity of Element X? A sodium B neon C phosphorous D copper Since it is a covalent molecule, it has to be a nonmetal. It cannot be neon since neon is an inert noble gas that would not react with chlorine.