Details of the three Sub-atomic (fundamental) Particles Particle Position Relative Mass Relative Charge Proton Nucleus 1 +1 Neutron Nucleus 1 0 Electron Orbitals 1/1800 -1 An atom of Lithium (Li) can be represented as follows: 7 3 Li Atomic Number Atomic Symbol Mass Number The atomic number, Z, is the number of protons in the nucleus. The mass number ,A, is the total number of protons and neutrons in the atom. Number of neutrons = A – Z Isotopes Isotopes are atoms of same element with the same number of protons, but different numbers of neutrons. Isotopes have similar chemical properties because they have the same electronic structure. They may have slightly varying physical properties because they have different masses. There are various
models for atomic
structure
models for atomic
structure
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2.1.1 Atomic structure and isotopes Learning outcomes Additional guidance Learners should be able to demonstrate and apply their knowledge and understanding of: Atomic structure and isotopes (a) isotopes as atoms of the same element with different numbers of neutrons and different masses (b) atomic structure in terms of the numbers of protons, neutrons and electrons for atoms and ions, given the atomic number, mass number and any ionic charge HSW1 Different models for atomic structure can be used to explain different phenomena, e.g. the Bohr model explains periodic properties. HSW7 The changing accepted models of atomic structure over time. The use of evidence to accept or reject particular models.