C1 And C2-Atomic Structure And Periodic Table

the smallest part of an element that can still be recognised as that element

A substance which is made up one atom and cannot be broken down.

Compounds are two or more elements chemically combined in fixed proportions and can be represented by formulae using symbols of the atoms from which they were formed.

Chemical reactions

A mixtures consists of two or more elements or compounds not chemically combined together.The chemical properties of each substance in the mixture are unchanged.

John Daltan, early 19th century- Dalton’s solid sphere- Atoms first described as solid spheres. Discovered that every organism was made of atoms and cannit be destroyed nor created

JJ thomson-1897-plum pudding model-the plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it.Discovery of the electrom

Ernest Rutherford 1909- Alpha scattering experiment- mass is concentrated at the centre; the nucleus is charged. Most of an atom is empty space and most of mass is in nucleus. Discovered the proton- Rutherford’s nuclear model

Niels Bohr 1913- Bohr’s planetary model- Niels bohr discovered how atoms can have a different number of shells. The electrons also have a fixed orbit around the nucleus and have set distances from the nucleus. All atoms must have the same number of protons and electrons. Does not collapse inwards by shells due to the attraction between the positive nucleus and negative electrons due to electrostatic force.

James chadwick-1940-discovered that there are nuetrons in the nucleus-Quantum atomic model

The experiment was the alpha scattering experment which was conducted to develop ideas of atomic strucure. A beam alpha atoms was shot towards a thin gold sheet. Some were defelcted, however most went through the sheet but changed direction. The few that were defelected at larger than 90° angles suggested there was a small, dense center within the middle of an atom, whilst the ones that went through but slightly changed course indicated that the positive alpha particles were repelled by the positively charged nucleus of atoms within the gold sheet. Most went directly through, suggesting most of the atom is empty space. This therefore concluded that atoms had a small, positive, dense center called a nucleus but most of the atom between the nucleus and electrons was empty space.

The number at the bottom which shows the number of protons and electrons.

The sum of the protons and nuetrons in an atom.This is the number at the top

Isotopes are distinct nuclear species of the same chemical element. They have the same atomic number and position in the periodic table, but different nucleon numbers due to different numbers of neutrons in their nuclei.

(Isotope 1 times abundance) +(isotope 2 times abundance) divided by 100

an arrangement of elements in the order of their atomic numbers, forming groups and periods

1864- Noticed periodicity based on elemental mass and sorted elements by mass • Law of Octaves- Every 8th (known) element was similar • Not similar properties in each group • Compounds • 2 in same box • Hydrogen not by itself

Dmitri Mendellev (1869) “Father of the periodic table”: • Also arranged elements by mass (atomic weight) and property but included empty spaces for irregular jumps in mass • These accounted for undiscovered elements of which he successfully predicted • Groups Hydrogen by itself but in a shared group • Still multiple elements in a single box

Elements that react to form positive ions-found at left of periodic table

Elements that do not form positive ions-found at right and top of periodic table

Alkali metals are soft, highly reactive with relatively low melting- boiling points. Alkali metals have large atomic radii between neighboring atoms of group 1 and show a weaker force of attraction due to which they are generally soft and thus have a low melting point. All group 1 elements have low densities.

Burns with a strongly red tinged flame and produces a white solid

Fizzes,disappears gradually Floats and moves around

Burns to give white solid Lithium+chlorine=lithium chloride