How many electrons are generally present in metals in their valence shell?
Metals generally have 1, 2 or 3 electrons in their outermost orbit or valence shell. e.g.,
The number of valence electrons in sodium, magnesium and aluminium metals are 1, 2 and 3 respectively.
How many electrons are present in non- metals in their outermost shell?
Non-metals generally contain 4,5,6,7 or 8 electrons in their outermost orbit or shell.
The number of valence electrons in carbon, nitrogen, oxygen and fluorine are 4, 5, 6, 7 respectively.
To which category do antimony and arsenic belong?
Elements which show the properties of both the metals and non-metals are called metalloids. e.g., antimony and arsenic
Identify the metal that replaces magnesium from its salt.
Calcium is more reactive than magnesium. Hence, Mg can be replaced from its salt by calcium.
Aluminium foil is used for wrapping food. On which property is it used?
Aluminium foil is prepared by beating it into sheets, i.e., property of malleability. Hence, aluminium foil is used for the given application.
Identify the non-metal which exhibits yellow colour.
Sulphur is yellow in colour.
Which of the following are the properties of non-metals?
(i) They have low densities
(ii) They have low melting points
(iii) They are poor conductors of electricity
Non-metals have low densities, low melting points and are poor conductors of electricity.
Which of the following non-metals exists in liquid state at room temperature?
Bromine is the only non-metal which exists in liquid state at room temperature.
Identify the metal that does NOT react with HCl
Copper, Mercury, Silver and Gold are less reactive than hydrogen. Hence, they cannot displace hydrogen from the compounds like dilute acids, water, etc.
Which metal reacts vigorously with HCl to produce salt and hydrogen?
Among the given metals, sodium is a highly reactive metal, so it reacts vigorously to form salt and hydrogen.
When non-metals combine with oxygen, what do they produce?
Non-metals form two types of oxides, they can be acidic or neutral oxides
Identify the oxide of a non-metal which is neutral.
Some oxides of non-metals are neutral. e.g., CO.
Phosphorus combines with oxygen to form oxides. How many types of oxides are formed by it?
Phosphorus combines with oxygen and forms two oxides phosphorus trioxide and phosphorus pentoxide.
Which of the following dissolves in water to form sulphuric acid?
Acidic oxides dissolve in water and form acids. Sulphur trioxide (SO3) reacts with water and produces sulphuric acid (H2SO4)SO3+H2O→H2SO4
Which of the following compounds is used to make photographic films?
Silver bromide, a compound of silver is used to make photographic films. When light falls on the film, it sets up a reaction which changes silver bromide to silver
Which material is used for making crucibles?
Crucibles are used in the laboratory to perform high temperature reactions. They should resist high heating (they should not break). For this purpose, a mixture of graphite (an allotrope of carbon) and clay is used to make crucibles.
Which non-metal is used in the treatment of rubber during the process of vulcani-sation?
Sulphur is used in the process of vulcanization. Rubber when treated with sulphur becomes harder than ordinary rubber, so it is used to make tyres.
Which of the following is called a noble metal?
Gold, silver and platinum do not combine readily with other elements to form compounds, so they are called noble metals.
Identify the metal which is soft.
Sodium has less density, hence it is soft and can be cut even with a knife.
Why is tungsten used as a filament in electric bulbs?
Metal tungsten is used as a filament in electric bulbs because it has a high melting point.