.whatsapp-float{
    position:fixed;

    bottom:1px;
    right:1px;  

    z-index:9999;
}

.whatsapp-float img{
    width:100px;   /* tamanho do ícone */
    height:100px;

    transition:0.3s;
}

.whatsapp-float img:hover{
    transform:scale(1.1);
}