Valence and Core Electrons Life on the Edge Valence and Core Electrons

Atoms The Atom is the smallest particle of a substance that can exist by itself or be combined with other atoms to form a molecule. Atoms of course are three dimensional and actually take up space in three dimensions

Atomic Models Atomic Models are used to understand atoms in a much more simplified way Represented in 2D and not to scale. Easier to draw

Electron Shells Are the levels around the nucleus where electrons can be found These are energy levels These levels are represented on models by spheres or circles

General Patterns of Electrons Based on your handout, what do lithium, sodium, and potassium all have in common Each has two electrons in the first shell One electron in the outermost shell

General Patterns of Electrons If you know what group an element is in, what can you predict about its electron arrangement? The number of electrons in the outer most shell

General Patterns of Electrons What does the period an element is in tell you about its electrons? The number of electron shells

General Patterns of Electrons How can you determine the arrangement of an element’s electron from the position in the periodic table The number of shells is the same as the period number The number of electrons in the outermost shell is the same as the group number The inner shells have 2 electrons in the first shell 8 electrons in the second shell, 8 electrons in the third shell for elements before the transition elements and 18 electrons in the third shell for elements after the transition elements

Key Points The atomic number of an element is the same as the total number of electrons As you go from one element to the next in the periodic table, the number of electrons increase by one. The number of electrons corresponds to the atomic number

Key Points The period (row) number of the element is the same as the number of electron shells As you go down the periodic table, from one period to the next, the number of electron shells increase by one. In the first period, the atoms have electrons in only one shell In the second period, the atoms have electrons in two shells In the fourth period, the atoms have electrons in four shells

Key Points For main-group elements, (non-transitional), the group number of the elements is the same as the number of electrons in the outermost shell Example: All Group 4A elements have 4 electrons in their outermost shell All Group 8A elements have 8 electrons in their outermost shell

Valence Shell The valence shell is the outermost shell in an atom

Valence Electron The valence electron is the electron located in the outermost electron shell of an atom Valence electron

Core Electrons The core electrons are all the other electrons in an atom that are not on the valence shell Valence electron

Do Valence and Core Electron Sheet

Valence and Core Electron sheet What patterns do you see in the number of valence electrons in the table? Valence electron same as group number Increase by one in the period, 1-8

Valence and Core Electron sheet How do the numbers of core electrons vary across the second row? They all remain at 2

Valence and Core Electron sheet Explain why there is a change in the number of core electrons across the fourth row There are ten transitional element between Ca and Ga, so ten more electrons get filled in

Key Question Why do elements in the same group in the periodic table have similar properties? Electrons occupy distinct areas around the nucleus called electron shells. The arrangement of electrons in these shells are highly predictable For main group elements, elements in the same group have the same number of valence electrons The number of valence electrons increase across a period The number of shells and the number of core electrons increase as you go down a group