Periodic Table of Elements -1 Keywords Periodic table الجدول الدوري Symbol الرمز Group المجموعة Period الدورة Atomic number العدد الذري Mass number العدد الكتلي

helium carbon nitrogen sodium silver oxygen mercury neodymium chlorine gold mercury oxygen hydrogen helium sodium niobium neodymium carbon

Elements Everything is made up of elements. Scientists have identified 90 naturally occurring elements Scientists also created about 28 others.

Elements The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe.

Periodic Table The periodic table organizes the elements in a particular way. The periodic table helps you to predict the properties of an element and how it can react.

Atomic Number This refers to how many protons an atom of that element has. No two elements, have the same number of protons.

Atomic number & Mass number On the periodic table we find elemental symbols like this: The largest number is called the “mass number” This number tells us the mass of an atom of this element. Q. Where does almost all the mass of the atom come from? The nucleus! Q. What particles were in the nucleus? Protons & Neutrons! Q. So what does the mass number also tells us? The sum of (protons + neutrons) Mass number 4 He 2 There are two numbers, one above the other below:

He Mass number 4 2 + - Proton Nucleus Neutron 2 protons + 2 neutrons = mass number of 4 So why is Helium’s mass number = 4? 2 x Proton + - 4 He 2 Nucleus 2 x Neutron

Mass Number The nucleus contains protons and neutrons. When you add up the numbers of protons and neutrons you get the mass of the atom! This is called the “Mass number”

Atomic Number Protons The atomic number tells us the number of ______________ Which is the same as the number of _________ + - Electrons Atoms have an equal number of positive protons and negative electrons. This is so the atom has no overall electrical charge. 4 He 2 Atomic Number

Look at the periodic table, what do you notice about the numbers?

H He Li Be Key fact! The number of protons defines the element! 1 H 4 He 2 7 Li 3 9 Be 4 The number of protons defines the element! Elements are arranged on the periodic table in order of their atomic numbers. If you change the number of protons (atomic number) you change the element!

He 4 2 Mass number Protons + Neutrons So how do we work out the number of neutrons? Mass number – atomic number = number of neutrons. 4 – 2 = 2 neutrons. Atomic number Protons Atomic number

Practice: Protons, Neutrons and Electrons Key maths skill 4 He 2 2 7 Li 3 3 31 P 15 15 Protons ______ Neutrons _____ Electrons _____ Protons ______ Neutrons _____ Electrons _____ Protons ______ Neutrons _____ Electrons _____ 2 4 16 2 3 15 23 Na 11 11 20 Ne 10 10 80 Br 35 35 Protons ______ Neutrons _____ Electrons _____ Protons ______ Neutrons _____ Electrons _____ Protons ______ Neutrons _____ Electrons _____ 12 10 45 11 10 35

Periodic Table of Elements – Lesson 2 Keywords Periodic table الجدول الدوري Symbol الرمز Group المجموعة Period الدورة Atomic number العدد الذري Mass number العدد الكتلي

Groups Columns of elements are called groups . have the same number of electrons on the outer shell Each horizontal row of elements is called a period. Elements that have the same number of shells.

Groups

Questions 1- Explain the difference between a Group and a Period 2-Elements

Alkali Metals Group 1 elements are also known as Alkali metals (You don’t need to remember that) Alkali metals are in group 1, which means that they have only 1 electron on the outer shell

Group 2 Earth Metals They have two electrons on the outer shell. Alkaline earth metals include magnesium and calcium, among others.

Group 7 - Halogens Group 7 elements are also called Halogens. How many electrons do they have on the outer shell?

Group 8- Noble Gases Elements in this group have a FULL outer shell.

TASK! Find the following elements Group 1 Period 2 _____________