IV. Answer the following:
15. Define atom.
16. Define molecule.
17. Define element.
18. Write any three difference between metals and non- metals.
19. Define metalloids.
20. What are compounds?
21. Classify the following as elements and compounds.
a. water b. common salt c. sugar
d. carbon dioxide
e. iodine f. lithium
22. Write the chemical formula and name the elements present in the following compounds
a. Water b. Sodium chloride c.carbondioxide d.calcium oxide.
23. Write any two properties of compound.
24. Define chemical formula
25. Define atomicity
26. Calculate the atomicity of H2 SO4
5
6.
7.
27. Calculate the atomicity of H20.
Answers
Answer:
15. Atoms are the basic units of matter and the defining structure of elements.
16.A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge.
17. each of more than one hundred substances that cannot be chemically interconverted or broken down into simpler substances and are primary constituents of matter. Each element is distinguished by its atomic number, i.e. the number of protons in the nuclei of its atoms.
18.1) all metals are solid at room temperature except mercury, which is a liquid at room temperature. ... 3) metals have high densities except lithium, soduim and potassium. 4) metals are malleable (can be beaten into thin sheets). 5) metals are ductile (can be drwn into wires).
19.an element (e.g. arsenic, antimony, or tin) whose properties are intermediate between those of metals and solid non-metals or semiconductors.
20.A compound is a material formed by chemically bonding two or more chemical elements.
Answer:
Atom : An atom can be defined as the smallest indivisible unit of an element which exhibits all the proporties of that element and may or may not be have independent existence.