FÍSICA Y QUÍMICA 3º DE E.S.O. FIRST TERM UNIT 2_2: CHEMICAL SUBSTANCES

Atomic number = Number of protons Henry Moseley in 1913, proposed to use the atomic number  as the organising principle of the elements Atomic number = Number of protons 2

The periodic table of elements https://www.youtube.com/watch?v=zGM-wSKFBpo

The horizontal rows are called periods. Elements on the periodic table are grouped according to their chemical properties. The horizontal rows are called periods. The vertical columns on the periodic table are called groups.

The groups are numbered one through 18. Sometimes they are called families.

Elements in each group have similar properties Elements in each group have similar properties. For example, in Group 11, copper, silver, and gold have similar properties. Each is a shiny metal. Each is a good conductor of electricity and heat

The chemical properties of an element are due to the distribution of electrons around the nucleus, particularly the outer, or valence, electrons The outermost shell of an atom is called its valence shell The electrons of the outermost shell are involved during chemical combinations, so that the valence shell is decisive during a chemical reaction.

The term REACTIVE indicates how likely an element is to undergo a chemical change. Most elements are somewhat reactive and combine with other materials.

The atoms of the elements in Groups 1 and 17 are reactive. The elements of Group 18 are the least reactive of all the elements.

The periodic table is a kind of map of the elements The periodic table is a kind of map of the elements. An element’s position on the periodic table indicates a lot about the properties and reactivity of this element

The periodic table has three main regions—metals on the left, nonmetals (except hydrogen) on the right, and metalloids in between

Most elements are metals. In general, metals are elements that conduct electricity and heat well and have a shiny appearance. Metals can be shaped easily. Except for mercury, which is a liquid, metals are solids at room temperature.

The elements to the right side are called nonmetals. The properties of nonmetals tend to be the opposite of those of metals. The properties of nonmetals also tend to vary more from element to element than the properties of the metals do.

The elements to the right side are called nonmetals. Many of them are gases at room temperature, and one—bromine—is a liquid. The solid nonmetals often have dull surfaces and cannot be shaped by hammering or drawing into wires. Nonmetals are generally poor conductors of heat and electric current.

Metalloids. Metalloids are elements that have properties of both metals and nonmetals. In the periodic table, they lie on either side of a zigzag line separating metals from nonmetals

Metalloids. Metalloids often make up the semiconductors found in electronic devices Silicon, gallium (Not a metalloid), and germanium are three semiconductors used in computer chips.

Some groups have special names.

In the portion of the periodic table below, fill in the atomic number, (2) the electron configuration, (3) the number of shells, and (4) the number of outer electrons. Copy the table in your notebook and fill in the gaps

In the portion of the periodic table below, fill in the atomic number, (2) the electron configuration, (3) the number of shells, and (4) the number of outer electrons. 1 2 1 3 2, 1 2 1 4 2, 2 2 5 2, 3 2 3 6 2, 4 2 4 7 2, 5 2 5 8 2, 6 2 6 9 2, 7 2 7 10 2, 8 2 8 11 2, 8, 1 3 1 12 2, 8, 2 3 2 13 2, 8, 3 3 14 2, 8, 4 3 4 15 2, 8, 5 3 5 16 2, 8, 6 3 6 17 2, 8, 7 3 7 18 2, 8, 8 3 8 19 2, 8, 8, 1 4 1 20 2, 8, 8, 2 4 2 Correct your answers

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Make your conclusions

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 The atomic number is the organising principle of the elements. So when going from left to right across a row Z increases by one, just as the number of protons

1 1 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 4 4 Make your conclusions

1 1 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 4 4 1) As we go from top to bottom down a group the number of shells increases by one. The number of the period tells us about the number of shells.

What do the elements in the same period have in common? 1 1 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 4 4 Make your conclusions

What do the elements in the same period have in common? 1 1 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 4 4 2) Elements across a series have the same number of shells, so that the elements in the same period have the same number of shells

Then, make your conclusions What do the elements in the same group have in common? 1 2 2, 1 1 2, 2 2 2, 3 3 2, 4 4 2, 5 5 2, 6 6 2, 7 7 2, 8 8 2, 8, 1 1 2, 8, 2 2 2, 8, 3 3 2, 8, 4 4 2, 8, 5 5 2, 8, 6 6 2, 8, 7 7 2, 8, 8 8 2, 8, 8, 1 1 2, 8, 8, 2 2 Then, make your conclusions

What do the elements in the same group have in common? 1 2 2, 1 1 2, 2 2 2, 3 3 2, 4 4 2, 5 5 2, 6 6 2, 7 7 2, 8 8 2, 8, 1 1 2, 8, 2 2 2, 8, 3 3 2, 8, 4 4 2, 8, 5 5 2, 8, 6 6 2, 8, 7 7 2, 8, 8 8 2, 8, 8, 1 1 2, 8, 8, 2 2 The elements within a group have the same number of outer electrons. The valance shell is identical in all the elements of the same group.

The chemical properties of an element are due to the valence, electrons because the electrons of the outermost shell are involved during chemical combinations The elements within a group have the same number of outer electrons. The valance shell is identical in all the elements of the same group. The elements within a group have the same chemical properties because they have the same number of valance electrons

What do the elements in the group of the inert gases have in common? Group 18 elements are called the noble, or inert, gases because they almost never react with other elements What do the elements in the group of the inert gases have in common?

What do all the elements in group of the inert gases have in common? All noble gases have the maximum number of electrons possible in their outer shell (2 for helium, 8 for all others). This makes them very stable, so that they do not form chemical compounds easily.

What do all the elements in group of the inert gases have in common? Having the outer shell fully occupied makes an element to be very stable

What do all alkaly elements have in common? The outer electron is very easily lost. This makes the ion very stable because it has the same electron configuration as a noble gas .

What do all alkaly elements have in common? Li    Li+ + 1 e- A neutral lithium (Li) has 3 protons and 3 electrons, and it is missing an electron. Then we have 3 protons and 2 electrons. So lithium loses one electron to become a 1+ cation

What do all alkaly elements have in common? Na    Na+ + 1 e- A neutral sodium (Na) loses one electron to become a 1+ cation

What do all alkaly elements have in common? Me    Me+ + 1 e- All alkaly metals lose one electron to become a 1+ cation

What do all alkaly earth metals have in common? The two outer electrons are very easily lost. This makes the ion very stable because it has the same electron configuration as a noble gas .

What do all alkaly earth metals have in common? Mg    Mg++ + 2 e- A neutral magnesium (Mg) loses two electrons to become a 2+ cation

What do all alkaly earth metals have in common? Me    Me++ + 2 e- All alkaly earth metals lose two electrons to become a 2+ cation

What do all halogens have in common? F + 1 e-    F- The outer shell gains an electron. This makes the ion very stable because it has the same electron configuration as a noble gas (Ne) .

What do all halogens have in common? F + 1 e-    F- A neutral fluorine F has 9 protons and 9 electrons, and it is gaining one electron. Then we have 9 protons and 10 electrons. So, fluorine gained one electron to become a 1- anion.

What do all halogens have in common? Cl + 1 e-    Cl- A neutral chlorine Cl chlorine gained one electron to become a 1- anion.

What do all halogens have in common? X + 1 e-    X- All neutral halogens gain one electron to become a 1- anion.

What do all the elements in group 16 have in common? O + 2 e-    O2- The outer shell gains two electrons. This makes oxygen very stable because it has the same electron configuration as the noble gas Ne.

What do all the elements in group 16 have in common? O + 2 e-    O2- A neutral atom in group 16 gains two electrons to become a 2- anion.

Look at the examples and decide the most common charge for the ions formed by the following elements: N, P, S, Se, I, Ca, Sr, K, Rb,

Typical ions for several groups in the periodic table Look at the examples and decide the most common charge for the ions formed by the following elements in the periodic table: N, P, S, Se, I, Ca, Sr, K, Rb, Typical ions for several groups in the periodic table

Predicting ion charges

Noble gases have no tendency to lose or to gain electrons Predicting ion charges Noble gases have no tendency to lose or to gain electrons

Noble gases have no tendency to lose or to gain electrons Predicting ion charges Noble gases have no tendency to lose or to gain electrons

Metals tend to lose electrons and form cations Predicting ion charges Metals tend to lose electrons and form cations

Non-metals tend to gain electrons and form anions Predicting ion charges Non-metals tend to gain electrons and form anions

Non-metals tend to gain electrons to become an anion. Noble gases have no tendency to lose or to gain electrons Non-metals tend to gain electrons to become an anion. Metals tend to lose the outer electrons to become a cation