1
The scientist who discovered that the nucleus of the atom contains positively charges protons
Rutherford
The scientist who added the zero group to his periodic table
Moseley
The number of elements in Mendeleev's periodic table
67
The unit of measuring the atomic radius
picometer
G.R.F.: The Scientists attempt to classify the elements?
To facilitate their study
to find a relation between the elements and their physical and chemical properties
Locate the 18Ar in the modern periodic table
Period 3
group zero
calculate the atomic number of the element that lies in period 3 group 3A
13
The most metallic element in the periodic table
Cesium Cs
G.R.F.: The atomic size decreases by increasing the atomic number in the period
due to the increase in the attraction between the positive protons and negative electrons
G.R.F.: Mendeleev left gaps in his periodic table?
Because he predicted the discovery of new elements
The series in which the metals are arranged in a descending order according to their chemical activity
chemical activity series
The elements that lie in the middle of the periodic table and take the symbol B
Transition elements
G.R.F.: Water is a polar compound?
Because the difference in the electronegativity between its elements are relatively high
G.R.F.: The elements of the same group have the same properties
because they have the same number of electrons in their outermost energy level
G.R.F.: Potassium 19K is a stronger metal than sodium 11Na?
Because it has a larger atomic size than sodium
What happens when:
A metallic atom loses one or more electrons during a chemical reaction?
It changes into a positive ion carrying positive charges equal the number of lost electrons
The ability of an atom of a covalent compound to attract electrons toward itself
Electronegativity
What's meant by:
Metalloids
They are elements that have the properties of both metals and non-metals
How to differentiate between copper and calcium?
ca: react very slowly with cold water
cu: don't react with water
Write the balanced chemical equation for:
Burning magnesium ribbon in the air
2Mg + O2 >>> 2MgO