English Chemistry

1. Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter.
Chemistry is chiefly concerned with atoms and molecules and their interactions and transformations, an atom is the smallest unit
of matter that defines the chemical elements which has a nucleus that is formed for protons and neutrons, for example, the
properties of the chemical bonds formed between atoms to create chemical compounds.
As you can see in this image 1.1 the Elements are ordered by its qualities like the elements of the fourth period
immediately after the first row of the transition metals have unusually small atomic radii because the 3d-electrons are not
effective at shielding the increased nuclear charge, and smaller atomic size correlates with higher electronegativity.
In 1789, Antoine Lavoisier published a list of 33 chemical elements,
grouping them into gases, metals, nonmetals, and earths. Chemists spent the
following century searching for a more precise classification scheme. In 1829,
Johann Wolfgang Döbereiner observed that many of the elements could be
grouped into triads based on their chemical properties. Lithium, sodium, and
potassium, for example, were grouped together in a triad as soft, reactive metals.
Döbereiner also observed that, when arranged by atomic weight, the second
member of each triad was roughly the average of the first and the third; this
became known as the Law of Triads. German chemist Leopold Gmelin worked with
this system, and by 1843 he had identified ten triads, three groups of four, and one
group of five. Jean-Baptiste Dumas published work in 1857 describing relationships
between various groups of metals. Although various chemists were able to identify
relationships between small groups of elements, they had yet to build one scheme
that encompassed them all.
Image 1.1 Periodic table trends (arrows
direct an increase)

2. 1. The nucleus of an atom consists of
A. electrons and neutrons
B. electrons and protons
C. protons and neutrons
D. All of the above
4. The element which has the smallest atomic radius among
the following is
A. Na B. H
C. Hg D. Pb
3. The most electronegative element among the following is
A. sodium B. bromine
C. fluorine D. oxygen
4. Who was the first chemists in grouping the elements
A. Svante Arrhenius B. Max Born
C. Amedeo Avogadro D. Antoine Lavoisier