الأسبوع 2 · الدرس الأول «تركيب الذرة» (٢): الرموز الكيميائية والعدد الذري والعدد الكتلي والنظائر · 3 دروس
1
Chemical symbols and their Latin roots
Science Prep 1 Term 1, Unit 1: pp. 6–9
GoalWrite and read the symbols of common elements and explain why some come from Latin names.
New words
symbol · one capital letter, or a capital and a small letter, that stands for an elementelement · a pure substance made of only one kind of atomfertiliser · a substance added to soil to give plants the elements they need
Explanation
Chemists all over the world write each element with a symbol: one capital letter, or a capital letter followed by one small letter. So carbon is C, nitrogen is N, chlorine is Cl and chromium is Cr. Always write the second letter small: Cl is chlorine, but CL is not a symbol. Many symbols come from the old Latin names of the elements, so they do not match the English name: sodium is Na (natrium), potassium is K (kalium), copper is Cu (cuprum) and iron is Fe (ferrum). In Arabic books the symbols stay Latin, so scientists in every country can read them. Gardeners meet three symbols on fertiliser bags: N, P and K. Nitrogen helps leafy green growth, phosphorus helps strong roots and potassium helps healthy growth.
Element
Symbol
Latin name
sodium
Na
natrium
potassium
K
kalium
copper
Cu
cuprum
iron
Fe
ferrum
Worked examples
Symbol
Element
C
carbon
Cl
chlorine
Cr
chromium
Nada writes Cl, Cr and C on three cards. All three start with C but they are three different elements: chlorine, chromium and carbon. The small second letter makes the difference.
A farmer reads N, P and K on a fertiliser bag. N is for nitrogen (green leaves), P is for phosphorus (strong roots) and K is for potassium (healthy growth). K comes from the Latin name kalium.
Too much fertiliser can wash off the fields into water and harm the living things there. Farmers and scientists therefore try to use only the amount that plants need. What do you think are the good and bad sides of using fertiliser?
Class activity
Symbol cards. Make eight cards with a symbol on one side (Na, K, Cu, Fe, C, N, Cl, Cr) and the name on the other. Play a memory game with a partner. For the four Latin ones, add the Latin name on a third line.
Practice
1
What is the symbol of sodium, and which Latin name does it come from?
Na, from natrium.
2
Which element has the symbol Fe?
Iron (from ferrum).
3
Is “CL” a correct symbol for chlorine? Explain.
No. The second letter must be small, so the symbol is Cl.
4
What does each letter of NPK on a fertiliser bag stand for?
N is nitrogen, P is phosphorus and K is potassium.
