1.1.1 - Atoms

Specification

1.1.1 Atoms

Assessable learning outcomes

Atomic structure

* The mass of an electron can be assumed to be 1/2000th the mass of a proton.
How Science Works 1, 7a:

* Modern development of the structure of the atom; the changing accepted view of the structure of the atom; acceptance (and Candidates should be able to:
(a) describe protons, neutrons and electrons in terms of relative charge and relative mass;
(b) describe the distribution of mass and charge within an atom;
(c) describe the contribution of protons and neutrons to the nucleus of an atom, in terms of atomic (proton) number and mass (nucleon) number;
rejection) of different theories for the structure of the atom from the Greeks, Dalton, Thompson and Rutherford, Moseley, et al.
(d) deduce the numbers of protons, neutrons and electrons in:
(i) an atom given its atomic and mass number,
(ii) an ion given its atomic number, mass number and ionic charge;
(e) explain the term isotopes as atoms of an element with different numbers of neutrons and different masses;

Relative masses

* For simple molecules, the term relative molecular mass will be used.
* For compounds with giant structures, the term relative formula mass will be used.
(f) state that 12C is used as the standard measurement of relative masses;

(g) define the terms relative isotopic mass and relative atomic mass, based on the 12C scale;

(h) calculate the relative atomic mass of an element given the relative abundances of its isotopes;

(i) use the terms relative molecular mass and relative formula mass and calculate values from relative atomic masses.

How Science Works 3:

* Use of spreadsheets in calculating relative atomic masses from data;
* Definitions of relative molecular mass and relative formula mass will not be required.

Atomic structure

Describe protons, neutrons and electrons in terms of relative charge and relative mass

  Proton Neutron Electron
Relative Charge +1 0 -1
Relative Mass 1 1 1/2000

Describe the distribution of mass and charge within an atom

Positively charged nucleus containing most of the mass, surrounded by atomic shells with orbiting electrons of negative charge and negligible mass.

Describe the contribution of protons and neutrons to the nucleus of an atom, in terms of atomic (proton) number and mass (nucleon) number.

The atomic number of the nucleus, also the proton number, shows the number of protons in the nucleus. It also defines the element. The number of neutrons added to the number of protons is the nucleon number or mass number.

Eg. 12C 6 - 12 is the nucleon number, and 6 is the proton number. The number of neutrons can be found by subtracting the atomic number from the nucleon number.

Deduce the numbers of protons, neutrons and electrons in:

The number of protons is equal to the atomic number, coincidentally so is the number of electrons in most elements. The number of neutrons can be found by subtracting the proton number from the mass number.

(i) an atom given its atomic and mass number. The element is always given by its proton number.

12C 6 is Carbon, however 14C 6 is also carbon, albeit an Isotope of carbon.

Explain the term isotopes.

Atoms with the same number of protons, although a different number of neutrons.


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Relative Masses

* For simple molecules, the term relative molecular mass will be used.
* For compounds with giant structures, the term relative formula mass will be used. State that 12C is used as the standard measurement of relative masses

Define the terms relative isotopic mass and relative atomic mass, based on the 12C scale;

Calculate the relative atomic mass of an element given the relative abundances of its isotopes

Mass per mole of a substance

(a) explain the terms:

(b) define and use the term molar mass (units g mol–1)

Use the terms relative molecular mass and relative formula mass and calculate values from relative atomic masses.


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