Elements, atomic structure, compounds and mixtures Flashcards
Is atomic number on the bottom or top?
Bottom
Is mass number on the bottom or top?
Top
How has the dalton model changed over time?
Due to discovery of subatomic particles
Structure of an atom?
Contains a nucleus that is tiny in comparison to the overall atom and contains protons and neutrons surrounded by electrons in shells
Protons
Relative charge;
Relative mass;
+1
1
Neutrons
Relative charge;
Relative mass;
0
1
Electrons
Relative charge;
Relative mass;
-1
0
Why do atoms contain equal numbers of protons and electrons?
Because then their charges ‘cancel out’ so that the electrical charge overall is neutral
Mass number is number of…?
Protons + neutrons
Atomic number is the number of…?
Protons (or electrons)
What are isotopes?
Atoms of the same element with the same number of protons but different numbers of neutrons
Why can isotopes cause the relative atomic mass to not be a whole number?
Because when we calculate the atomic mass of an element as a weighted average of isotopic masses in relation to their natural abundance the number tends to be a decimal
The periodic table is an arrangement of elements in order of….?
Atomic number
What are groups in the periodic table?
Columns - elements in the same groups have the same number of electrons in their outer shells
What are periods?
Rows - Same number of electron shells
What are groups?
Columns - Same number of electrons in their outer shells
What is relative atomic mass?
The average mass of an atom compared to 1/12 of the mass ^12C
What factors increase the R of R?
Increase temperature
increase concentration
increase surface area
add a catalyst
What did John Dalton’s theory state?
Atoms are tiny invisible particles
atoms of one element are all the same
atoms of different elements are different
compounds are formed by combining atoms
what did J.J. Thomson discover?
That atoms are made from even smaller things, he discovered electrons with cathode rays. He likened atoms to plum puddings
What did Ernest Rutherford disover?
The atom was 99% space, there must be a very dense centre - he called this the nucleus - which contained positive particles. Electrons must be outside the nucleus.
What did James Chadwick discover?
a neutral particle - neutron
What did Niels Bohr discover?
Electrons surrounded the nucleus in shells
In Rutherfords experiment why did most alpha particles pass straight through the gold atom?
because most of an atom (99%) is just open space
Why do some of the alpha particles deflect or bounce back in Rutherfords experiment?
there must be a very dense positive nucleus
what can you use to measure the volume of gas more accurately?
use a gas syringe
