Answer:
(a) (i) All the elements of a group have similar chemical properties because they have same no. of valence electrons in their outermost shell. (ii) All the elements of a period have different chemical properties because they have different no. of valence electrons in their atoms.
The answer is C. Glue gun melts a glue stick.
Answer:
The correct answer is <em>D) Niels Bohr</em>
Explanation:
Bohr proposed a new atomic model, whereby he explains that electrons rotate around the nucleus at well-defined levels, describing circular orbits. Each orbit was called the energy level (it is called the main quantum number n, going from numbers 1 to 7). To make his model, Bohr studied the Hydrogen atom (it has a proton in its nucleus and an electron rotating around it).
Answer: The mole ratio of oxygen to pentane for the combustion of pentane is 8 : 1.
Explanation: The given reaction is a type of combustion reaction.
Combustion reaction is a reaction in which a hydrocarbon reacts with oxygen gas to produce water and carbon dioxide gas.
For the reaction of pentane with oxygen, the balanced equation would be:
In the reaction, 1 mole of 
reacts with 8 moles of 
gas.
Thus giving us the mole ratio as
Oxygen : Pentane = 8 : 1
The STP is Standard temperature and pressure.
Standard temperature is defined as zero degrees Celsius (0° C)
Standard pressure supports 760 millimeters in a mercurial barometer (760 mmHg)
we have that
760 mmHg= 1 atm
therefore
the answer is 0 deg C and 1 atm.
