CIE Chemistry Paper-1: Specimen Questions 29 - 30 of 99
Question number: 29
The diagram shows the structure of an atom.
Which diagram shows the structure of an isotope of this atom?
Isotopes are variants of a particular chemical element which differ in neutron number, although all isotopes of a given element have the same number of proton in each atom. The number of protons within the atom’s nucleus is called atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons.
Question number: 30
Astatine is an element in Group VII of the Periodic Table. It has only ever been produced in very small amounts.
What are the likely properties of astatine?
colour = dark brown, state = gas, reaction with aqueous potassium iodide = brown colour
colour = green, state = solid, reaction with aqueous potassium iodide = no reaction
colour = black, state = solid, reaction with aqueous potassium iodide = no reaction
colour = yellow, state = liquid, reaction with aqueous potassium iodide = brown colour
The properties of astatine have been estimated based on its periodic table position as a heavier analog of iodine, and a member of the halogens.
Halogens get darker with increasing atomic weight – fluorine is nearly colorless, chlorine is yellow-green, bromine is red-brown, and iodine is dark gray/violet. Astatine is sometimes described as probably being a black solid (assuming it follows this trend), or as having a metallic appearance (if it is a metalloid or a metal)
Also, Reactivity in group 17, the halogens, decreases as you move down the group. Since astatine is lower in the group than iodine, astatine is least reactive among halogens.