hi everyone welcome to igcs study bu where you can revise chemistry topics from the Cambridge IGCSE syllabus if you are enjoying our video so far please don't forget to hit the like button and subscribe to our channel in this video you are going to learn part one of topic 8 the periodic table the periodic table is a table that arranges All chemical elements in a way that can help us predict their physical properties and chemical reactions let's first learn about how these elements are arranged the elements of the periodic table are arranged in rows called periods and columns called groups just a quick Rec cap the elements in the periodic table are displayed with their atomic number which is the number of protons they have and their relative atomic mass so the elements in the periodic table are organized in order of increasing proton number which is also known as the atomic number the atomic number increases from left to right across each period and from Top to bottom down each group for example lithium has three protons berium has four boron has five and so on the proton number is the smaller number near each symbol periods are the horizontal rows in the periodic table numbered 1 to 7 the period number indicates the number of electron shells an atom has let's take lithium for example its atomic number is three so its electron configuration is 2 1 remember there can be a maximum of two electrons in the first shell eight in the second and eight in the third since there are two shells used we know that lithium belongs to period two so in the elements of period two like lithium and oxygen the atoms have two electron shells in Period three like sodium and chlorine they have three and so on As you move from left to right across a period in the periodic table the character of The Elements change from metallic to non-metallic you may have noticed the red stepped line on this periodic table this line separates metals from non-metals with the non-metals to the right except for hydrogen so on the left side of the periodic table as shown in blue for illustration are the metals and on the right side of the periodic table as shown in Peach for illustration are the non-metals metals are elements that tend to lose electron to form positive ions in chemical reactions metals are typically good conductors of heat and electricity they have a shiny appearance they are malleable and ductile which means that they can be shaped or bent they generally have high melting and boiling points non-metals are elements that tend to gain or sh electrons to form negative ions or calent Bonds in chemical reactions non-metals are typically poor conductors of heat and electricity they have a dull appearance they are brittle in solid form and they generally have low melting and boiling points so as you go across a period elements gradually lose metallic characteristics and gain non-metallic characteristics we will learn more about Metals in the next chapter groups are the vertical columns in the periodic table groups show how many outer electrons each atom has let's take lithium for example its atomic number is three so its electron conf configuration is 2 1 since there is one electron in its outer shell we know that lithium belongs to group one so group one elements have one electron in their outer electron shell group two elements have two electrons in their outer shell and so on the elements in the last group that is group eight or group zero however are an exception to this rule as they have two or eight electrons in their outer electron shell next group number an ion charge the group number of an element in the periodic table is related to the number of electrons in its outermost shell and helps determine the charge of the ions it forms elements in groups 1 to three have one two or three electrons in the their outermost shell they tend to lose these electrons to achieve a full outer shell forming positive ions or cations remember in chapter 2 we learned that it is easier for elements to lose electrons than to gain them when they have fewer electrons in their outer shell group one elements have one electron in their outer shell and forms one plus ions example na plus group two elements have two electrons in their outer shell and forms two plus ions example ca2+ and group three elements have three electrons in their outer shell and forms 3+ ions example al3+ elements in groups 5 to 7 have five six or seven electrons in their outermost shell they tend to gain electrons to achieve a full outer shell forming negative ions or anions remember in chapter 2 we learned that it is easier for elements to gain electrons than to lose them when they have more electrons in their outer shell in group five elements have five electrons in the outer shell and forms three minus ions example in 3 minus in group six they have six electrons in their outer shell and forms 2 minus ions example O2 minus and in group seven they have seven electrons in the outer shell and forms one minus ions example cl1 minus in group zero these elements have a full outer shell of electrons they are generally stable and do not form ions easily in summary the group number indicates the number of electrons in the outermost shell and whether the element will lose or gain electrons to form ions next similar properties in group elements the outer electrons are mainly responsible for the chemical properties of any element and therefore elements in the same group have similar chemical properties this is because they have the same number of electrons in their outermost shell this similar outer electron Arrangement leads to similar ways of reacting with other elements this is because in a reaction it is the outermost electrons that participate in the chemical reaction for example all elements in group one have one electron in their outer shell making them react in a similar way with water the position of an element in the periodic table can be used to predict its properties based on its group and period this is because the periodic table has patterns or Trends in how elements are arranged and these patterns help us predict how elements will behave these Trends can be seen Down groups and across periods some of the properties of elements that we can predict using the periodic table are boiling point melting point density and reactivity let's consider the elements in group one as an example lithium is at the top of group one sodium is below lithium and potassium is below sodium so if we consider the reactivity Trend down the group reactivity increases as you go down the group lithium reacts with water relatively slowly sodium reacts more vigorously with water based on this we can predict that potassium will be even more reactive than lithium and sodium lastly identifying Trends in groups if we observe the reactions of say the group one Metals with water we will notice that lithium reacts slowly with water produces fizzing and moves on the surface sodium reacts more vigorously than lithium with more fizzing and faster movement pottassium reacts even more vigorously burns with a lilac flame and moves rapidly based on the above observations we may identify a trend occurring as you go down the group that reactivity of group one Metals increases as you move down the group now given this information about the first three elements of the group we may predict that the lower group one Metals will react even more strongly and this may be confirmed by observing their reactions with water rubidium reacts very violently with Sparks the reaction is more vigorous compared to pottassium and cesium causes a violent explosion overall the pattern shows that Metals at the bottom of group one are more reactive than those at the top that concludes part one of topic 8 the periodic table are you enjoying our videos are they helping you here's a way you can show your appreciation and support our continued efforts you may use YouTube super thanks to 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