Chemistry - atoms and chemical reactions

Atomic number is defined as

• Number of electrons

• Number of protons

• Number of neutrons

• Number of protons + neutrons

Atomic mass depends on the number of

• Protons

• Neutrons

• Protons and Neutrons

• Electrons

An atom has no net charge due to

• Its subatomic particles carrying no electrical charge

• The positively charged protons cancel out the negatively charged neutrons

• The positively The positively charged neutrons cancel out the negatively charged electrons

• The positively The positively charged protons cancel out the negatively charged electrons

Why is it called a chemical "equation"?

• The number of atoms of the elements before the reaction is equal to the number of atoms after the reaction

• The total mass of the reacting elements would be the same as the total mass of whatever products are formed

• The reaction produces an equal number of products to the number of elements which react

• You MUST write an equals sign

In a chemical reaction...

• The original substances disappear and are replaced by new substances

• The original substances remain but are joined by new substances

• Bonds are broken and atoms are rearranged to make new substances

• The atoms of the original substances break down and new atoms are made

What is the energy input required to start a reaction?

• Activation energy

• Thermal energy

• Heat energy

• Electrical energy

What is the word equation for a neutralisation reaction?

• acid + base → salt + hydrogen + water

• acid + base → water

• acid + base → salt + water

• acid + base → salt + carbon dioxide + water

Which is correct...

• Most of the mass of an atom is concentrated towards the outside

• That the mass of an atom is equally distributed

• The the mass of an atom is concentrated in the centre of the atom

• The masses of atoms are so small that are not important

Which is exothermic?

• Condensation

• Baking soda and vinegar

• Combustion

• Photosynthesis

A negative ion...

• Has an equal number of protons and electrons

• It has more electrons than protons

• It has a different number of neutrons

• It has more protons than electrons