2.1 - Atomic Structure And Isotopes Flashcards
What are the 3 important things to remember with atoms?
• No. of protons and electrons in an atom are always equal
• The no. Of energy levels in an atom = its period number
• the no. Of electrons in an atoms outer energy level = its group number
Define isotope
Atoms of the same element with the same number of protons but a different number of neutrons and different mass number
What are the similarities and differences of isotopes?
• same chemical properties
• same physical properties
• different masses
• The mass number of an isotope is known as its relative isotopic mass
Define ion
An atom or molecule with a net electronic charge due to the loss or gain of electrons
Why do ions form?
When atoms lose or gain electrons to create electronic stability by creating a fuller outer energy level
What do metals do?
Lose electrons to form positive ions
What do non metals do?
Gain electrons to form negative ions
Define relative atomic mass
The weighted mean mass of an atom of a element compared to 1/12th of the mass of an atom of carbon 12
Define relative molecular mass
The weighted mean mass of a molecule compared with 1/12th of the mass of an atom of carbon 12
Define relative formula mass
The weighted mean mass of a formula unit compared to 1/12th of the mass of an atom of carbon 12
What is m/z?
Mass to charge ratio
What was stated in daltons atomic theory?
• atoms are tiny particles made of elements
• atoms cannot be divided
• all the atoms in an element are the same
• atoms of one element are different to those of other elements
What did Thompson discover about electrons?
• they have a negative charge
• they can be deflected by magnet and electric field
• they have very small mass
Explain the plum pudding model?
Atoms are made up of negative electrons moving around in a sea of positive charge
What were Rutherford proposal after the gold leaf experiment?
• most of the mass and positive charge of the atom are in the nucleus
• electrons orbit the nucleus
• most of atoms volume is the space between the nucleus and the electrons
• overall positive and negative charges must balance
Explain the current model of the atom
• protons and neutrons are found in the nucleus
• electrons orbit in shells
• nucleus is tiny compared to the total volume of atom
• most of atoms mass is in the nucleus
• most of the atom is empty space between the nucleus and the electrons
Define relative istopic mass
The mass of an atom of an isotope compared with 1/12 th of the mass of an atom of carbon-12
What 2 assumptions are made when calculating mass number?
- Contribution of the electron is neglected
- Mass of both proton and neutron is taken as 1.0 U
What are the uses of mass spectrometry?
• identify unknown compounds
• find relative abundance of each isotope of an element
• determine structural information
How does mass spectrometer work?
• sample is made into positive ions
• they pass through the apparatus and are separated according to mass to charge ratio
• A computer analyses the data and produces mass spectrum
What are the 4 elements that don’t tend to form ions and why?
• Beryllium, Boron , Carbon and silicon
• requires a lot of energy to transfer outer shell electrons
What are molecular ions?
Covalently bonded atoms that lose or gain electrons
What is the charge of an ammonium ion?
+1
What is the charge of a hydroxide ion?
-1
What is the charge of a nitrate ion?
-1
What is the charge of a carbonate ion?
-2
What is the charge of a sulfate ion?
-2
What is an empirical formula?
Simplest whole number ratio of atoms of each element present in a compound
What is meant by the term weighted mean mass ?
The mean mass taking into account the relative abundancies of the isotopes
