8 th grade science

Isotones Atomic number(Z) MassNumber(A) Electrons(e) Proton(p) Neutron(n) 14 C 6 6 14 6 6 8(14-6) 15 N 7 7 15 7 7 8(15-7) 16 O 8 8 16 8 8 h..

Question: On what basis is Potassium (z = 19) placed in 4 th period and 1 st group? Answer: The electronic configuration of potassium is 2, 8, 8, 1. It has four shells so it belongs to the 4 th period. The 4 th period has elements wit..

Valence electrons of an atom are responsible for chemical reactions as they take part in them. Elements having same number of valence electrons in their atoms possess similar chemical properties. All alkali metals have one valence electron in their atom. Thus, their chemical properties are simil..

The elements placed in group 7 (VIIA) of the periodic table are called halogens or salt producers. All these elements form salts called halides, e.g. NaCl, NaI, KCl, KI etc. Halogen is an ancient Greek word meaning 'salt producer'. Halogens have seven electrons in their valence shell and so are mo..

This law could be best applied, only up to the element calcium. Newly discovered elements could not fit into the octave structure. The feature of resemblance of the 8 th element when arranged in increasing order of their atomic mass was not successful with heavier elements...

Name of the Crop Name of Disease Symptoms Control Measure Rice Blast Brown boat-shaped lesions appear on the leaves Seed treatment with thiram solution in water. Spray bavistin at 10 days interval Wheat Rust Yellow, brown or black elongated spots appear on leaves Sp..

Commodities Crops Varieties Cereals Rice Ir36, Pusa Basmati 1, Kasturi, Vikas, PNR-591-18 Wheat HD2678, HD2285, C306, PBW154, HW157 Maize Ganga 5, H1M128, Shakti, Navjot, Vikram Pulses Chickpea K850, H208, Pusa 240, Pant 114 Pigeonpea..

(Inert gases are indicated in blue) Element Symbol Atomic number Electronic configuration (or Electron arrangement) K L M N Hydrogen H 1 1 Helium He 2 2 Lithium Li 3 2,1 Beryllium Be 4 2,2 Boron B 5 2,3 Carbon C 6 2,4 Nitrogen N 7 2,5 Oxygen O 8 2..

Sl. No Name in English Name in any other Language other than English Symbol 1. Lithium - Li 2. Sodium Natrium (latin) Na 3. Magnesium - Mg 4. Aluminium - Al 5. Potassium Kalium (latin) K 6. Calcium - Ca 7. Vanadium - V 8. Chromium -..

. The eighth element from nitrogen is phosphorus and both these elements are similar in properties. Based on this observation, Newland stated his law of octaves thus 'when elements are arranged in increasing order of their atomic mass, the eighth element resembles the first in physical and chemical..