In this presentation you will
This presentation is the property of its rightful owner.
Sponsored Links
1 / 23

In this presentation you will: PowerPoint PPT Presentation


  • 37 Views
  • Uploaded on
  • Presentation posted in: General

In this presentation you will:. Chemical Reactions and Valence Electrons. Cl -. Na +. explore how chemical reactions depend on valence electrons. Next >. Introduction. During a chemical reaction, chemicals combine to create different chemicals.

Download Presentation

In this presentation you will:

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


In this presentation you will

In this presentation you will:

Chemical Reactions and Valence Electrons

Cl-

Na+

  • explore how chemical reactions depend on valence electrons

Next >


Introduction

Introduction

During a chemical reaction, chemicals combine to create different chemicals.

These reactions can produce very different substances.

For example, if a liquid and a solid were added together, a liquid and a gas might be produced.

Next >


Valence electrons

Valence Electrons

Each atom that takes part in a reaction has a nucleus, with one or more electrons orbiting that nucleus.

Valence electron

The electrons exist in different orbits called shells.

Ni

The more electrons an atom has, the more shells are occupied.

Valence electron

The electrons in the outermost shell are called the valence electrons.

Next >


Valence electrons1

Valence Electrons

Since the valence electrons are the outermost electrons, they are the nearest part of the atom to other atoms.

The valence electrons are also furthest from the nucleus, so the force holding them to the nucleus is the weakest.

Valence electrons

If these electrons gain just a small amount of energy, they can move from the outer shell of one atom to the outer shell of another.

Next >


Valence electrons2

Valence Electrons

Each shell has a maximum number of electrons it can contain.

Each shell is divided into a number of sub-shells.

p sub-shell

A full outer shell or sub-shell is a very stable configuration.

Shell 2

Neon

s sub-shell

s sub-shell

For example, the atoms of inert gases, like neon, have full outer sub-shells and are very unlikely to react with other atoms.

p sub-shell

Next >


Valence electrons3

Valence Electrons

When electrons move between shells they try and achieve this stable configuration.

An element with only one electron in its outermost sub-shell is likely to easily lose this electron in a reaction with other atoms.

The single electron would be most likely to go to an incomplete sub-shell.

Next >


Valence electrons and the periodic table

Valence Electrons and the Periodic Table

The Periodic Table can show us how many electrons each element has.

Group 1 elements, the alkali metals, have one valence electron.

Group 2 metals, the alkaline earth metals, have two valence electrons.

Group 18 elements, the noble gases, have eight valence electrons.

Group 17 elements, the halogens, have seven valence electrons.

Next >


Valence electrons and the periodic table1

Valence Electrons and the Periodic Table

Group 1 and 2 metals are highly reactive because they can lose their valence electrons easily.

Magnesium – Group 2

Group 18 elements are almost non-reactive (inert). They have a full outer shell of electrons.

Neon – Group 18

Fluorine – Group 17

Group 17 elements are very reactive because they have 1 space in their outermost shell. They can easily capture an extra electron to fill the shell.

Next >


Valence electrons and charge

Valence Electrons and Charge

Normally, the sum of charges in an atom of an element is zero.

This is because the number of protons is the same as the number of electrons.

28 electrons

28 protons

A proton carries a single positive charge, and an electron carries a single negative charge of the same value.

Ni

If an electron is gained or lost, then the balance of charges is no longer the same. The atom is positively or negatively charged.

Next >


Valence electrons and charge1

Valence Electrons and Charge

If the atom has lost an electron, it becomes positively charged.

17 photons

18 electrons

11 photons

10 electrons

Positive ion

Negative ion

If the atom has gained an electron, it becomes negatively charged.

Next >


Valence electrons and charge2

Valence Electrons and Charge

These charged atoms, now called ions, will be attracted to oppositely charged ions and repelled by similarly charged ions.

The attraction force forms an ionic bond and creates a new chemical.

Attraction

Repulsion

Next >


Valence electrons and charge3

Valence Electrons and Charge

Alternatively, the valence electrons may not totally move across and join another atom.

Instead the atoms may share each other’s valence electrons.

This sharing of valence electrons is called a covalent bond.

Next >


Examples

Examples

Sodium and chlorine bond ionically to form sodium chloride.

The single valence electron from sodium will join the outer shell of chlorine and fill that sub-shell.

There is then an electrostatic attraction between the two ions.

Next >


Examples1

Examples

Four hydrogen atoms (each with one valence electron) and one carbon atom (4 valence electrons) share their electrons. This creates methane, CH4, which has four covalent bonds.

This sharing gives all the atoms a full shell of electrons.

Next >


Question 1

Question 1

Which electrons are involved in bonding?

A) Valence electrons

B) Innermost electrons

C) Most energetic electrons

D) Shell electrons

Next >


In this presentation you will

Question 1

Which electrons are involved in bonding?

A) Valence electrons

B) Innermost electrons

C) Most energetic electrons

D) Shell electrons

Next >


Question 2

Question 2

What is a positive ion?

A) An atom with an equal number of protons and electrons

B) An atom that has lost an electron

C) An atom that has more electrons than protons

D) An atom that has gained an electron

Next >


In this presentation you will

Question 2

What is a positive ion?

A) An atom with an equal number of protons and electrons

B) An atom that has lost an electron

C) An atom that has more electrons than protons

D) An atom that has gained an electron

Next >


Question 3

Question 3

Two chemicals can react to form a new chemical when:

A) an electron of one atom changes place with the electron of another atom

B) all the atoms lose their outermost electrons in ionic bonding

C) electrons of one element change places with the protons of the other element

D) an atom of one element gives up its electron to join the atom of the other element

Next >


In this presentation you will

Question 3

Two chemicals can react to form a new chemical when:

A) an electron of one atom changes place with the electron of another atom

B) all the atoms lose their outermost electrons in ionic bonding

C) electrons of one element change places with the protons of the other element

D) an atom of one element gives up its electron to join the atom of the other element

Next >


Question 4

Question 4

Covalent bonding is when:

A) atoms of different elements bond by sharing an outermost electron

B) atoms of different elements bond by one element giving up an outermost electron to the other

C) electrons of one element change places with the protons of the other element

D) an atom of one element gives up its electron to join the atom of the other element

Next >


In this presentation you will

Question 4

Covalent bonding is when:

A) atoms of different elements bond by sharing an outermost electron

B) atoms of different elements bond by one element giving up an outermost electron to the other

C) electrons of one element change places with the protons of the other element

D) an atom of one element gives up its electron to join the atom of the other element

Next >


Summary

Summary

In this presentation you have seen:

  • how chemical reactions depend on valence electrons

End >


  • Login